Left-wing populism

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Left-wing_populism

An Occupy Wall Street sign with the 99% slogan, a left-wing populist movement.

Left-wing populism, also called social populism, is a political ideology that combines left-wing politics with populist rhetoric and themes. Its rhetoric often includes elements of anti-elitism, opposition to the Establishment, and speaking for the "common people". Recurring themes for left-wing populists include economic democracy, social justice, and scepticism of globalization. Socialist theory plays a lesser role than in traditional left-wing ideologies.

Criticism of capitalism and globalization is also linked to unpopular United States military operations, especially those in the Middle East. It is considered that the populist left does not exclude others horizontally and relies on egalitarian ideals. Some scholars also speak of nationalist left-wing populist movements, a feature exhibited by the Sandinista Revolution in Nicaragua or the Bolivarian Revolution in Venezuela. Unlike exclusionary or right-wing populism, left-wing populist parties are generally supportive of minority rights, as well as to an idea of nationality that is not delimited by cultural or ethnic particularisms. Bernie Sanders and Alexandria Ocasio-Cortez, self-described democratic socialists, are examples of modern left-wing populist politicians in the United States. With the rise of Syriza and Podemos during the European debt crisis, there has been increased debate on new left-wing populism in Europe.

Traditionally, left-wing populism has been associated with the socialist movement; since the 2010s, there has been a movement close to left-wing populism in the left-liberal camp, some of which are considered social democratic positions. Left-liberal economic populism appealing to the working class has been prominent in some countries, such as with Joe Biden of United States and Lee Jae-myung of South Korea, in the 2020s, where liberal and conservative parties are the main two parties.

By country

Africa

Burkina Faso

Main article: Sankarism

Egypt

Main article: Nasserism

Ghana

Main article: Nkrumaism

Libya

Main article: Gaddafi loyalism

Nigeria

Peter Obi, a businessman and outsider politician running with the Labour Party in the 2023 Nigerian presidential election, was seen as a populist politician, gaining the support of much of Nigeria's youth. Before running for President, Obi took part in the End SARS movement, which sought to disband Nigeria's Special Anti-Robbery Squad, or SARS due to its connection to the criminal underworld and its excessive use of force. SARS was disbanded in 2020. Obi's presidential campaign in 2022 and 2023 constantly ran on issues such as economic development, fighting corruption, moving beyond ethnic politics, which have dominated Nigeria going back to its founding, and promoting criminal justice reform. Obi sought to challenge the traditional two-party system, led by the centrist and Buharist All Progressives Congress on one side, and the center-right, nationalist, and conservative-liberal Peoples Democratic Party.

South Africa

Julius Malema, the former leader of the African National Congress Youth League, broke away from the center-left African National Congress to form the Economic Freedom Fighters. The EFF are notable for their extreme black nationalism, which includes anti-Asian racism, anti-White racism, and antisemitism. This also includes radical economic reforms inspired by Marxism-Leninism, including land reform without compensation. The EFF is also extremely anti-West, to the point of actively trying to support Russian imperialism in Ukraine and Chinese imperialism within Africa itself. However, unlike many similar left-wing populist parties that have a hard-right approach to race, the EFF is not socially conservative. In fact, voters for the EFF are the mostly likely of all voters in South Africa to support same-sex marriage, which has been legal since 2006.

In the run-up to the 2024 South African general election, former president Jacob Zuma has formed his own political party, uMkhonto we Sizwe. Named after the former paramilitary wing of the ANC of the same name, Zuma has been trying to position himself as supporting a more legitimate version of the ANC. MK, as Zuma's party is also known, calls for deporting illegal immigrants to South Africa, land reform without compensation, and opposition to same-sex marriage.

Tanzania

Main article: Ujamaa

Uganda

Main article: Move to the Left

Zimbabwe

Dictator Robert Mugabe and his ZANU–PF party are seen as populist by many observers. Mugabe's ideology combined African nationalism with socialist economics and a broad-based appeal to the people. The most notably policies of ZANU–PF are their land reforms.

Americas

Argentina

Néstor Kirchner (left) and Cristina Fernández de Kirchner (right) served as Presidents of Argentina from 2003–2007 and 2007–2015.

 

 

Main article: Kirchnerism

Cristina Fernández de Kirchner (the President of Argentina from 2007 to 2015) and her husband Néstor Kirchner were said to practice Kirchnerism, a variant of Peronism that was often mentioned alongside other Pink tide governments in Latin America. During Cristina Fernández de Kirchner's time in office, she spoke against certain free trade agreements, such as the proposed Free Trade Area of the Americas. Her administration was characterized by tax increases, especially on agricultural exports during the late 2000s commodities boom, Argentina's main export, in order to fund social programs such as the PROGRESAR university scholarships, the universal allocation per child subsidy (commonly referred to as AUH in Argentina, Asignación Universal por Hijo), a means-tested benefit to families with children who qualified for the subsidy, and progressive social reforms such as the recognition of same-sex marriage.

Bolivia

The leadership of Siles Zuazo practised left-wing populism as well as that of former socialist President Evo Morales.

Brazil

Main article: Lulism

Lulism is a pragmatic centre-left ideology to the extent that it is called "socialist neoliberalism", but it appeals to a progressive, common-class image and also has populist elements in terms of popular mobilization.

Ecuador

Rafael Correa, the former President of Ecuador, has stressed the importance of a "populist discourse" and has integrated technocrats to work within this context for the common Ecuadorians. Correa has blamed foreign non-governmental organizations for exploiting the indigenous people in the conflict between the indigenous peoples and the government.

Mexico

Andrés Manuel López Obrador in 2018

The current President of Mexico, Andrés Manuel López Obrador (or AMLO for short), and his governing party, the National Regeneration Movement, are considered left-wing populist in nature. AMLO has been a politician in Mexico for over three decades. He has been described as many different things, including center-left, progressive, a left-wing populist, social democratic, and economically nationalist.

United States

Bernie Sanders in 2020

See also: Congressional Progressive Caucus, Democratic Socialists of America, and Justice Democrats

The People's Party (United States), commonly known as the Populists, was a economically liberal movement, primarily agrarian in nature. They cast themselves in opposition to big business, particularly the railroads, and the political establishment controlled by them. It advocated for government intervention in the economy, such as the government ownership of railroads.

Huey Long, the Great Depression-era Governor-turned-Senator of Louisiana, was one of the first modern American left-wing populists in the United States. He advocated for wealth redistribution under his Share Our Wealth plan, which had its roots in the classical left-wing populist movement of Jacksonian democracy, which is related to the radical movement.

Meanwhile, Bernie Sanders and Alexandria Ocasio-Cortez, self-described democratic socialists, are examples of modern left-wing populist politicians. Sanders and Ocasio-Cortez's populist message tend to place the people in opposition to big business and the very wealthy. Ocasio-Cortez's Democratic primary victory over the establishment Democratic Caucus Chair Joe Crowley, a 10-term incumbent, was widely seen as the biggest upset victory in the 2018 midterm election primaries. The Nation magazine described Ocasio-Cortez as a "new rock star" who was "storming the country on behalf of insurgent populists." Elizabeth Warren are also mentioned as a representative left-wing or liberal populist, and Warren is sometimes evaluated as a social democrat. Joe Biden is usually classified as a political moderate, but his economic policies occasionally have attracted the populist moniker.

Venezuela

Main article: Chavismo

The presidency of Hugo Chávez resembled a combination of folk wisdom and charismatic leadership with doctrinaire socialism. Chávez was often rather fond of conspiracy theories, especially those which portrayed America as an evil actor in the world out to get Venezuela and the developing world. Anti-Americanism was crucial to Chávez's populism, even though Venezuela's history is somewhat unique compared to the rest of Latin America. During the Cold War, Venezuela both had a democratically-elected socialist president and good relations with the United States. Nonetheless, this did not deter Chávez from using anti-Americanism to distract from his regime's economic incompetence, especially when it came to managing inflation.

Asia

Israel

Main articles: 2011 Israeli social justice protests and 2023 Israeli judicial reform protests

Stav Shaffir is a politician who was traditionally associetate with the more left-wing and populistic elements of Israeli politics, especially issues of environmentalism, social justice, and a strongly pro-peace stance to the Israeli-Palestinian conflict. She initially got her start in Israeli politics as one of the three leaders, alongside Daphni Leef and Itzik Shmuli, of the 2011 social justice protests. Shaffir became particularly well known for her debate with Likud MK Miri Regev over housing prices on the Israeli television program Erev Hadash. She would go on to discuss the protest movement on tours to the United States, alongside pro-peace Labor Zionist Amos Oz, serving as a keynote speaker for Jewish-American organizations like JStreet.

In 2012, Shaffir joined the Israeli Labor Party. She became a member of the Israeli Knesset after the 2013 Israeli legislative election. She worked with the socially liberal, secular, and liberal Zionist party Hatnua, eventually forming the Zionist Union, which would also run in the 2015 Israeli legislative election. By that time, however, she had left and become the leader of the Green Movement, later renamed to the Green Party in 2019. For the September 2019 Israeli legislative election, Shaffir organized various parties together to form the Democratic Union coalition. However, after the 2020 Israeli legislative election, Shaffir lost her seat. During her tenure as MK from 2013 to 2020, Shaffir worked on issued from social justice to transfering settlements, and from government transparency efforts to LGBT rights.

Yesh Atid is a radical centrist or liberal party. In Israeli politics, "liberal" is not particularly a concept that is distinguished by left or right, but Yesh Atid is evaluated that it has a left-wing populist element in part. They criticize elitism that causes political corruption and demand a position on material redistribution. However, Yesh Atid has an element of economic liberalism simultaneously.

Former Aluf in the IDF Yair Golan has promoted views supporting Leftist Zionism, a two-state solution with Israel keeping the settlement blocs, full separation of synagogue and state as well as ending the marriage monopoly by the Chief Rabbinate, opposing corruption, supporting the 2023 judicial reform protests, supporting LGBTQ+ rights, and creating a fairer economy for all Israelis.

Tarō Yamamoto in 2020. He is mentioned as a (left-wing) liberal-populist.

Japan

Reiwa Shinsengumi, led by Tarō Yamamoto, is a representative Japanese left-wing populist movement. While he and his party use anti-established rhetoric, they are sometimes called "liberal populist". According to experts, Yamamoto uses a simple message to spotlight single individuals left behind, including people struggling with poverty or non-permanent employment, who used to devote themselves to radical conservatism.

Reiwa Shinsengumi is also called a "progressive populist", because they are not rooted in the traditional Japanese socialist or Labor movement, but are culturally and economically progressive, representing marginalized young people and minorities.

South Korea

South Korea's leftist political party, the Progressive Party, advocates direct democracy, anti-neoliberalism and anti-imperialism. They support a national liberalist foreign policy hostile to Japan.

Lee Jae-myung, one of DPK's major politicians, has been mentioned as a "populist" in some media outlets. Lee Jae-myung pledged to implement the world's first universal basic income system if elected in the 2022 South Korean presidential election but said he would not pay for it if the people opposed it. South Korea's right-wing politician Hong Joon-pyo saw Lee Jae-myung in September 2021 and accused him of being "Chávez of Gyeonggi Province". However, there is controversy in South Korea as to whether Lee Jae-myung can be viewed as a "left-wing populist" in the context of the United States or Europe. He once said he was "conservative" and suggested policies far from general left-wing populism in the United States and Europe, partially insisting on economic liberal policies such as deregulating companies on some issues. In addition, he showed a somewhat conservative tendency on some social agendas. In addition, Kim Hyun-jong, the head of the International Trade Special Division at the Lee Jae-myung Camp, met with Henry Kissinger, and Henry Kissinger gave Lee Jae-myung a handwritten autograph called "Good wishes". In addition, Lee Jae-myung's political orientation was somewhat ambiguous, so conservative journalist Dong-A Ilbo denied that he was a left-wing politician, while South Korea's far-left organization Workers' Solidarity evaluated him as a social democratic. (However, another South Korean left-wing undongkwon group denied that Lee Jae-myung is not a social democratic.) Lee is also a staunch supporter of free trade, unlike ordinary economic populists.

Europe

France

Jean-Luc Mélenchon, founder and leader of La France Insoumise

France has a long tradition of left-wing populism. During the French Revolution, the Hébertists, founded by Jacques Hébert in 1791, were a radical faction within the Society of the Friends of the Rights of Man and of the Citizen, a jacobin group leading France during the Reign of Terror. They were most known for their militant opposition to the more moderate leadership of Georges Danton and supported decristianization. They were also supportive of sending Louis XVI to the guillotine. Eventually, the Committee of Public Safety threatening, eventually charging Hébert with conspiracy and sending him to the guillotine.

In the modern day, La France Insoumise, or "France Unbowed" is a left-wing populist, democratic socialist, and eco-socialist party. The party is led by its founder, the populist firebrand Jean-Luc Mélenchon.

Germany

See also: Bündnis Sahra Wagenknecht

Oskar Lafontaine, member of The Left

The Party of Democratic Socialism was explicitly studied under left-wing populism, especially by German academics. The party was formed after the reunification of Germany, and it was similar to right-wing populists in that it relied on anti-elitism and media attention provided by charismatic leadership. The party competed for the same voter base with the right-wing populists to some extent, although it relied on a more serious platform in Eastern Germany. This was limited by anti-immigration sentiments preferred by some voters, although the lines were, for example, crossed by Oskar Lafontaine, who used a term previously associated with the Nazi Party, Fremdarbeiter ("foreign workers"), in his election campaign in 2005. The PDS merged into the Left Party in 2007. The Left Party is also viewed as a left-wing populist party, but it is not the basis of the party as a whole.

Greece

Alexis Tsipras of the Greek Syriza party

Syriza, which became the largest party since January 2015 elections, has been described as a left-wing populist party after its platform incorporated most demands of the popular movements in Greece during the government-debt crisis. Populist traits in Syriza's platform include the growing importance of "the People" in their rhetoric and "us/the people against them/the establishment" antagonism in campaigning. On immigration and LGBT rights, Syriza is inclusionary. Syriza itself does not accept the label "populist".

Ireland

Sinn Féin is generally considered an Irish republican, Irish nationalist, democratic socialist, and left-leaning populist political party.

Italy

The Italian Five Star Movement (M5S), which became the largest party in the 2018 general election, has often been described as a big tent populist party, but sometimes also as a left-wing populist movement; the "five stars", which are a reference to five critical issues for the party, are public water, sustainable transport, sustainable development, right to Internet access, and environmentalism, typical proposals of left-wing populist parties. However, despite its background in left-wing politics, the M5S has often expressed right-wing views on immigration.

In September 2019, the M5S formed a government with the centre-left Democratic Party (PD) and the left-wing Free and Equal (LeU), with Giuseppe Conte at its head. The government has been sometimes referred to as a left-wing populist cabinet.

Netherlands

The Socialist Party has run a left-wing populist platform after dropping its communist course in 1991. Although some have pointed out that the party has become less populist over the years, it still includes anti-elitism in its recent election manifestos. It opposes what it sees as the European superstate.

Spain

Pablo Iglesias, leader of Podemos

The left-wing populist party Podemos achieved 8% of the national vote in the 2014 European Parliament election. Due to avoiding nativist language typical of right-wing populists, Podemos can attract left-wing voters disappointed with the political establishment without taking sides in the regional political struggle. In the 2015 election for the national parliament, Podemos reached 20.65% of the vote and became the third largest party in the parliament after the conservative People's Party with 28.71% and the Spanish Socialist Workers' Party with 22.02%. In the new parliament, Podemos holds 69 out of 350 seats, which has resulted in the end of the traditional two-party system in Spain. In a November 2018 interview with Jacobin, Íñigo Errejón argues that Podemos requires a new "national-popular" strategy to win more elections.

Left-wing populist political parties

Active left-wing populist parties or parties with left-wing populist factions

Main article: List of populists

Represented in national legislatures

•  Argentina – Union for the Homeland
•  Australia – Queensland Greens
•  Belgium – Workers' Party of Belgium
•  Bulgaria – Bulgarian Socialist Party
•  Bosnia – Alliance of Independent Social Democrats
•  Bolivia – Movement for Socialism
•  Brazil – Workers' Party, Communist Party of Brazil, Socialism and Liberty Party
•  Chile – Broad Front (factions), Chile Digno
•  Colombia – Alternative Democratic Pole, Colombia Humana
•  Cyprus – Progressive Party of Working People
•  Denmark – Red–Green Alliance, Inuit Ataqatigiit, Republic
•  Dominican Republic – Dominican Liberation Party (factions)
•  Ecuador – Citizen Revolution Movement
•  Europe – Party of the European Left, The Left in the European Parliament – GUE/NGL
•  Estonia – Estonian Centre Party
•  Finland – Left Alliance
•  France – La France Insoumise
•  Germany – The Left
•  Greece – Syriza
•  Haiti – Platfòm Pitit Desalin
•  Honduras – Libertad y Refundación (Libre)
•  India – Communist Party of India (Marxist), Communist Party of India
•  Indonesia – Indonesian Democratic Party of Struggle
•  Ireland –  Northern Ireland – Sinn Féin, People Before Profit–Solidarity
•  Italy – Democratic Party (factions), Five Star Movement (factions)
•  Japan – Reiwa Shinsengumi
•  Luxembourg – The Left
•  Mexico – National Regeneration Movement, Labor Party
•  Mongolia – Mongolian People's Party
•  Netherlands – Socialist Party
•  Nicaragua – Sandinista National Liberation Front
•  Norway – Red Party
•  Paraguay – Guasú Front
•  Peru – Free Peru
•  Poland - Left Together, Your Movement
•  Portugal – Left Bloc
•  Romania – Social Democratic Party
•  Russia – Communist Party of the Russian Federation (factions), For a New Socialism
•  San Marino – United Left, Active Citizenship
•  Serbia – Socialist Party of Serbia, Movement of Socialists
•  Slovakia – Direction - Social Democracy
•  South Africa – Economic Freedom Fighters
•  South Korea - Progressive Party
•  Spain – Podemos, Más País, United Left
•  Sweden – Left Party
•  Turkey – Peoples' Democratic Party, Workers' Party of Turkey
•  United Kingdom – Workers Party of Britain,  Labour Party (factions)
•  United States – Democratic Party (factions), Democratic Socialists of America
•  Venezuela – United Socialist Party of Venezuela
•  Zimbabwe – ZANU–PF

Not represented in national legislatures

•  Austria – Communist Party of Austria
•  Chile – Equality Party, Progressive Party
•  Czechia – Communist Party of Bohemia and Moravia, The Left
•  Estonia – Estonian United Left Party
•  Finland – Communist Party of Finland
•  Germany – Sahra Wagenknecht Alliance — Reason and Justice
•  Greece – Popular Unity
•  India – Samajwadi Party, Rashtriya Janata Dal
•  Indonesia – Just and Prosperous People's Party, New Labour Party
•  Italy – Communist Refoundation Party, Democracy and Autonomy, Power to the People
•  Iran – People's Mujahedin of Iran
•  Malaysia – Socialist Party of Malaysia
•  Namibia – Namibian Economic Freedom Fighters
•  Russia – Patriots of Russia, Left Bloc, Left Front, Russian Socialist Movement
•  Serbia – Party of the Radical Left
•  Slovakia – Socialists.sk
•  Taiwan – New Power Party
•  Turkey – Patriotic Party (Turkey)
•  Ukraine – Communist Party of Ukraine
•  United Kingdom – Scottish Socialist Party, Northern Independence Party Transform

Pox party

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Pox_party

Pox parties, also known as flu parties, are social activities in which children are deliberately exposed to infectious diseases such as chickenpox. Such parties originated to "get it over with" before vaccines were available for a particular illness or because childhood infection might be less severe than infection during adulthood, according to proponents. For example, measles is more dangerous to adults than to children over five years old. Deliberately exposing people to diseases has since been discouraged by public health officials in favor of vaccination, which has caused a decline in the practice of pox parties, although flu parties saw a resurgence in the early 2010s.

Another, more modern, method of intentional contagion involves shipping infectious material. In many parts of the world, shipping infectious items is illegal or tightly regulated.

Effectiveness and risk

Parents who expose their children to varicella zoster virus in this manner often do so out of the belief that acquiring immunity to chickenpox via infection is safer and more effective than receiving a vaccination. Similar ideas have been applied to other diseases such as measles. Pediatricians have warned against holding pox parties, however, citing dangers arising from possible complications associated with chickenpox, such as encephalitis, chickenpox-associated pneumonia, and invasive group A strep. These serious complications (e.g., brain damage or death) are vastly more likely than vaccine adverse events. Before the chickenpox vaccine became available, 100 to 150 children in the U.S. died from chickenpox annually. In the UK, chickenpox vaccinations are not routine, and around 25 people die a year from the disease, with 80% of victims being adults, in the late 1990s. The chickenpox vaccine is now recommended by health officials, citing vastly superior safety when compared with infection.

Some parents have attempted to collect infectious materials, such as saliva, licked lollipops, or other infected items from people who claimed to have children infected with chickenpox. Others use social networking services to make contact with these strangers. The unknown person then mails the potentially infectious matter to the parent, who would then give it to their child in the hope that the child will become infected.

These practices are unlikely to reliably transmit the chickenpox virus because varicella zoster cannot survive for long on the surface of such items. The virus can, however, transmit other diseases, including hepatitis B, group A streptococcal infection, and staphylococcal infections — dangerous diseases to which the parents never intended to expose their children. Additionally, in the United States, deliberately sending infectious matter through the U.S. Postal Service is illegal.

While chickenpox parties are still held today, they are far less common than before the chickenpox vaccine was introduced.

History

In the United States, chickenpox parties were popularized before the introduction of the varicella vaccine in 1995. Children were also sometimes intentionally exposed to other common childhood illnesses, such as mumps and measles. Before vaccines for these infections became available, parents regarded these diseases as almost inevitable.

Flu parties

During the 2009 swine flu pandemic in Canada, doctors noted an increase in what was termed flu parties or flu flings. These gatherings, as with the pox parties, were designed explicitly to allow a parent's children to contract the "swine flu" influenza virus. Researchers such as Dr. Michael Gardam noted that because the pandemic was caused by a flu subtype to which very few people were previously exposed, parents would be just as likely to contract the disease and further its spread. Although these events were heavily discussed in the media, very few were confirmed to have happened.

COVID-19 party

A COVID-19 party (also called coronavirus party, corona party, and lockdown party) is a gathering held with the intention of catching or spreading COVID-19. It is a type of pox party where the intentional spread of disease is chosen to build up post-infection immunity. Parties have been reported to occur during the omicron wave, due to the belief that omicron causes only mild infection. Experts caution that infection with COVID runs the risk of hospitalization, and increasingly common side effects such as MIS-C and long COVID.

A number of news reports in the United States have suggested that parties have occurred with this intention early in the pandemic. However, such reports appear to involve sensational and unsubstantiated media coverage or misleading headlines which misrepresent the content of an article. Such stories have been compared to urban legends.

In the Netherlands, the term "coronavirus party" and other similar terms may refer to a party that is organized during the COVID-19 pandemic but without any intention of spreading the virus. As the party occurs during the COVID-19 pandemic, it may involve breaking existing regulations and restrictions to prevent COVID-19 infections (i.e., on people gatherings).

History

Street party in Copenhagen, Denmark, with police (middle) telling people to leave due to restrictions

In March 2020 Andy Beshear, the governor of Kentucky, reported that young people were taking part in parties and later testing positive for COVID-19. "The partygoers intentionally got together 'thinking they were invincible' and purposely defying state guidance to practice social distancing," he said. A CNN headline on 25 March 2020 stated, "A group of young adults held a coronavirus party in Kentucky to defy orders to socially distance. Now one of them has coronavirus." On the same day NPR published the headline "Kentucky Has 39 New Cases; 1 Person Attended A 'Coronavirus Party'". Both headlines misrepresented the content of the article and the quotes they used from Beshear who did not mention intentional parties for catching COVID-19, but rather that young people were attending parties and becoming sick with COVID-19.

On 6 May, The Seattle Times reported that Meghan DeBold, director of the Department of Community Health in Walla Walla, Washington, said that contact tracing had revealed people wanting to get sick with COVID-19 and get it over with had attended COVID parties. DeBold is quoted as saying "We ask about contacts, and there are 25 people because: 'We were at a COVID party'". An opinion piece for The New York Times by epidemiologist Greta Bauer on 8 April 2020 said she had heard "rumblings about people ... hosting a version of 'chickenpox parties'... to catch the virus". Rolling Stone states that Bauer did not cite "direct evidence of the existence of these parties." The New York Times reported on 6 May 2020 that stories such as the Walla Walla Covid Party "may have been more innocent gatherings" and county health officials retracted their statements.

On 23 June, Carsyn Leigh Davis was said to have died from COVID-19 at the age of 17 after her mother took her to a COVID party at her church, despite Carsyn having a history of health issues, including cancer. However, according to the coroner's report, there is no mention of a COVID party but rather a church function with 100 children where she did not wear a mask and where social distancing protocols were not followed. According to David Gorski, writing for Science-Based Medicine, the church party was called a "Release Party" and there is no evidence that the party was held so that people could intentionally catch COVID-19.

Response

Some news agencies consider COVID-19 parties to be a myth. Rolling Stone called "shaming people on the internet for not properly socially distancing" the favorite new American pastime. They state that these headlines are meant to be virally shared, and they considered the reality to be that young people had simply attended parties where they caught COVID-19, rather than deliberately attending them to contract COVID-19. Rolling Stone attributed the popularity of the stories to "generational animosity" and said that the coronavirus party stories "gives people cooped up in their homes a reason to pat themselves on the back and congratulate themselves for their own sacrifices". The Seattle Times article from Walla Walla backtracked the day after publishing their COVID-19 party story by stating they may not have been accurate.

Wired criticized reports on CNN and others of supposed college students in Tuscaloosa, Alabama throwing parties with infected guests then betting on the contagion that ensues. "They put money in a pot and they try to get Covid," said City Council member Sonya McKinstry, who was the story's lone source. "Whoever gets Covid-19 first gets the pot. It makes no sense." Wired says that these stories spread like a game of telephone with "loose talk from public officials and disgracefully sloppy journalism". "It is, of course, technically impossible to rule out the existence of Covid-19 parties. Maybe somewhere in this vast and complex nation, some foolish people are getting infected on purpose. It is also possible that the miasma of media coverage will coalesce into a vector of its own, inspiring Covid parties that otherwise would not have happened. But so far there's no hard evidence that even a single one has taken place—just a recurring cycle of breathless, unsubstantiated media coverage."

Investigator Benjamin Radford researched the claims from the media and stated that there was nothing new to these stories, and that the folklore world has seen stories of people believing that being inoculated against smallpox may turn people into cows. These stories cycle through social media, and include "poisoned Halloween candy, suicide-inducing online games, Satanists, caravans of diseased migrants, evil clowns, and many others." Other childhood diseases such as chickenpox and measles in years before vaccines to prevent these illnesses, some parents would hold 'pox parties' which Radford claims are still "often promoted by anti-vaccination groups". "Assuming you have a willing and potentially infectious patient (who's not bedridden or in a hospital)" holding a COVID-19 party would be problematic for many reasons, including not knowing if someone has COVID-19 or the flu as well as not knowing a person's viral load, according to Radford. He described the entire premise of the parties as "dubious".

All stories reported in the media had "all the typical ingredients of unfounded moral panic rumors", according to Radford. This includes teachers, police, school districts, governors "who publicize the information out of an abundance of caution. Journalists eagerly run with a sensational story, and there's little if any sober or skeptical follow-up". On 10 July 2020, a WOAI-TV station from San Antonio, Texas ran a story interviewing the Chief Medical Officer of Methodist Healthcare, Dr. Jane Appleby, who according to WOAI said she had heard from someone that a patient told their nurse right before dying that they had attended a COVID party to see if the virus was real or not, and now they regretted attending the party. Radford considers the stories "classic folklore (a friend-of-a-friend or FOAF) tale presented in news media as fact", noting that they were often anonymous third-hand story with no verifiable names or other details. He described the "deathbed conversation" ending to the story as being a "classic legend trope".

Money market

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Social_distancing

 
The money market is a component of the economy that provides short-term funds. The money market deals in short-term loans, generally for a period of a year or less.

As short-term securities became a commodity, the money market became a component of the financial market for assets involved in short-term borrowing, lending, buying and selling with original maturities of one year or less. Trading in money markets is done over the counter and is wholesale.

There are several money market instruments in most Western countries, including treasury bills, commercial paper, banker's acceptances, deposits, certificates of deposit, bills of exchange, repurchase agreements, federal funds, and short-lived mortgage- and asset-backed securities. The instruments bear differing maturities, currencies, credit risks, and structures. A market can be described as a money market if it is composed of highly liquid, short-term assets. Money market funds typically invest in government securities, certificates of deposit, commercial paper of companies, and other highly liquid, low-risk securities. The four most relevant types of money are commodity money, fiat money, fiduciary money (cheques, banknotes), and commercial bank money. Commodity money relies on intrinsically valuable commodities that act as a medium of exchange. Fiat money, on the other hand, gets its value from a government order.

Money markets, which provide liquidity for the global financial system including for capital markets, are part of the broader system of financial markets.

Participants

The money market consists of financial institutions and dealers in money or credit who wish to either borrow or lend. Participants borrow and lend for short periods, typically up to twelve months. Money market trades in short-term financial instruments commonly called "paper". This contrasts with the capital market for longer-term funding, which is supplied by bonds and equity.

The heart of the money market revolves around the concept of interbank lending, where banks lend and borrow from each other using financial instruments such as commercial paper and repurchase agreements. These instruments are often valued with reference to the London Interbank Offered Rate (LIBOR) for the specific term and currency.

Finance companies usually secure their funding by issuing substantial amounts of asset-backed commercial paper (ABCP). This paper is backed by the commitment of valuable assets placed into an ABCP conduit. These assets can include things like auto loans, credit card receivables, residential or commercial mortgage loans, mortgage-backed securities, and other financial assets. Some large, financially stable corporations even issue their own commercial paper, while others prefer to have banks issue it on their behalf.

In the United States, federal, state and local governments all issue paper to meet funding needs. States and local governments issue municipal paper, while the U.S. Treasury issues Treasury bills to fund the U.S. public debt:

• Trading companies often purchase bankers' acceptances to tender for payment to overseas suppliers.
• Retail and institutional money market funds
• Banks
• Central banks
• Cash management programs
• Merchant banks

Functions

Money markets serve five functions—to finance trade, finance industry, invest profitably, enhance commercial banks' self-sufficiency, and lubricate central bank policies.

Financing trade

The money market plays a crucial role in financing domestic and international trade. Commercial finance is made available to the traders through bills of exchange, which are discounted by the bill market. The acceptance houses and discount markets help in financing foreign trade.

Financing industry

The money market contributes to the growth of industries in two ways:

• They help industries secure short-term loans to meet their working capital requirements through the system of finance bills, commercial papers, etc.
• Industries generally need long-term loans, which are provided in the capital market. However, the capital market depends upon the nature of and the conditions in the money market. The short-term interest rates of the money market influence the long-term interest rates of the capital market. Thus, money market indirectly helps the industries through its link with and influence on long-term capital market.

Profitable investments

The money market enables commercial banks to use their excess reserves in profitable investments. The main objective of commercial banks is to earn income from its reserves as well as maintain liquidity to meet the uncertain cash demand of its depositors. In the money market, the excess reserves of commercial banks are invested in near money assets (e.g., short-term bills of exchange), which are easily converted into cash. Thus, commercial banks earn profits without sacrificing liquidity.

Self-sufficiency of commercial banks

Developed money markets help commercial banks to become self-sufficient. In an emergency, when commercial banks have scarcity of funds, they need not approach the central bank and borrow at a higher interest rate. They can instead meet their requirements by recalling their old short-run loans from the money market.

Help to central bank

Though the central bank can function and influence the banking system in the absence of a money market, the existence of a developed money market smooths the functioning and increases the efficiency of the central bank.

Money markets help central banks in two ways:

• Short-run interest rates serve as an indicator of the monetary and banking conditions in the country and, in this way, guide the central bank to adopt an appropriate banking policy,
• Sensitive and integrated money markets help the central bank secure quick and widespread influence on the sub-markets, thus facilitating effective policy implementation

Instruments

• Certificate of deposit – Time deposit, commonly offered to consumers by banks, thrift institutions, and credit unions.
• Repurchase agreements – Short-term loans—normally for less than one week and frequently for one day—arranged by selling securities to an investor with an agreement to repurchase them at a fixed price on a fixed date.
• Money market mutual funds - short-term investment debt, operated by professional institutions. Money market mutual funds are an investment fund where a number of investors invest their money in mutual fund institutions, and they diversify the funds in various investments.
• Commercial paper – Short term instruments promissory notes issued by company at discount to face value and redeemed at face value
• Eurodollar deposit – Deposits made in U.S. dollars at a bank or bank branch located outside the United States.
• Federal agency short-term securities – In the U.S., short-term securities issued by government sponsored enterprises such as the Farm Credit System, the Federal Home Loan Banks and the Federal National Mortgage Association. Money markets is heavily used function.
• Federal funds – In the U.S., interest-bearing deposits held by banks and other depository institutions at the Federal Reserve; these are immediately available funds that institutions borrow or lend, usually on an overnight basis. They are lent for the federal funds rate.
• Municipal notes – In the U.S., short-term notes issued by municipalities in anticipation of tax receipts or other revenues
• Treasury bills – Short-term debt obligations of a national government that are issued to mature in three to twelve months
• Money funds – Pooled short-maturity, high-quality investments that buy money market securities on behalf of retail or institutional investors
• Foreign exchange swaps – Exchanging a set of currencies in spot date and the reversal of the exchange of currencies at a predetermined time in the future
• Short-lived mortgage- and asset-backed securities

Discount and accrual instruments

There are two types of instruments in the fixed income market that pay interest at maturity, instead of as coupons—discount instruments and accrual instruments. Discount instruments, like repurchase agreements, are issued at a discount of face value, and their maturity value is the face value. Accrual instruments are issued at face value and mature at face value plus interest.

Herd immunity

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Herd_immunity

The top box shows an outbreak in a community in which a few people are infected (shown in red) and the rest are healthy but unimmunized (shown in blue); the illness spreads freely through the population. The middle box shows a population where a small number have been immunized (shown in yellow); those not immunized become infected while those immunized do not. In the bottom box, a large proportion of the population have been immunized; this prevents the illness from spreading significantly, including to unimmunized people. In the first two examples, most healthy unimmunized people become infected, whereas in the bottom example only one fourth of the healthy unimmunized people become infected.

Herd immunity (also called herd effect, community immunity, population immunity, or mass immunity) is a form of indirect protection that applies only to contagious diseases. It occurs when a sufficient percentage of a population has become immune to an infection, whether through previous infections or vaccination, thereby reducing the likelihood of infection for individuals who lack immunity.

Once the herd immunity has been reached, disease gradually disappears from a population and may result in eradication or permanent reduction of infections to zero if achieved worldwide. Herd immunity created via vaccination has contributed to the reduction of many diseases.

Effects

Protection of those without immunity

Some individuals either cannot develop immunity after vaccination or for medical reasons cannot be vaccinated. Newborn infants are too young to receive many vaccines, either for safety reasons or because passive immunity renders the vaccine ineffective. Individuals who are immunodeficient due to HIV/AIDS, lymphoma, leukemia, bone marrow cancer, an impaired spleen, chemotherapy, or radiotherapy may have lost any immunity that they previously had and vaccines may not be of any use for them because of their immunodeficiency.

A portion of those vaccinated may not develop long-term immunity. Vaccine contraindications may prevent certain individuals from being vaccinated. In addition to not being immune, individuals in one of these groups may be at a greater risk of developing complications from infection because of their medical status, but they may still be protected if a large enough percentage of the population is immune.

High levels of immunity in one age group can create herd immunity for other age groups. Vaccinating adults against pertussis reduces pertussis incidence in infants too young to be vaccinated, who are at the greatest risk of complications from the disease. This is especially important for close family members, who account for most of the transmissions to young infants. In the same manner, children receiving vaccines against pneumococcus reduces pneumococcal disease incidence among younger, unvaccinated siblings. Vaccinating children against pneumococcus and rotavirus has had the effect of reducing pneumococcus- and rotavirus-attributable hospitalizations for older children and adults, who do not normally receive these vaccines. Influenza (flu) is more severe in the elderly than in younger age groups, but influenza vaccines lack effectiveness in this demographic due to a waning of the immune system with age. The prioritization of school-age children for seasonal flu immunization, which is more effective than vaccinating the elderly, however, has been shown to create a certain degree of protection for the elderly.

For sexually transmitted infections (STIs), high levels of immunity in heterosexuals of one sex induces herd immunity for heterosexuals of both sexes. Vaccines against STIs that are targeted at heterosexuals of one sex result in significant declines in STIs in heterosexuals of both sexes if vaccine uptake in the target sex is high. Herd immunity from female vaccination does not, however, extend to males who have sex with males. High-risk behaviors make eliminating STIs difficult because, even though most infections occur among individuals with moderate risk, the majority of transmissions occur because of individuals who engage in high-risk behaviors. For this reason, in certain populations it may be necessary to immunize high-risk individuals regardless of sex.

Evolutionary pressure and serotype replacement

Herd immunity itself acts as an evolutionary pressure on pathogens, influencing viral evolution by encouraging the production of novel strains, referred to as escape mutants, that are able to evade herd immunity and infect previously immune individuals. The evolution of new strains is known as serotype replacement, or serotype shifting, as the prevalence of a specific serotype declines due to high levels of immunity, allowing other serotypes to replace it.

At the molecular level, viruses escape from herd immunity through antigenic drift, which is when mutations accumulate in the portion of the viral genome that encodes for the virus's surface antigen, typically a protein of the virus capsid, producing a change in the viral epitope. Alternatively, the reassortment of separate viral genome segments, or antigenic shift, which is more common when there are more strains in circulation, can also produce new serotypes. When either of these occur, memory T cells no longer recognize the virus, so people are not immune to the dominant circulating strain. For both influenza and norovirus, epidemics temporarily induce herd immunity until a new dominant strain emerges, causing successive waves of epidemics. As this evolution poses a challenge to herd immunity, broadly neutralizing antibodies and "universal" vaccines that can provide protection beyond a specific serotype are in development.

Initial vaccines against Streptococcus pneumoniae significantly reduced nasopharyngeal carriage of vaccine serotypes (VTs), including antibiotic-resistant types, only to be entirely offset by increased carriage of non-vaccine serotypes (NVTs). This did not result in a proportionate increase in disease incidence though, since NVTs were less invasive than VTs. Since then, pneumococcal vaccines that provide protection from the emerging serotypes have been introduced and have successfully countered their emergence. The possibility of future shifting remains, so further strategies to deal with this include expansion of VT coverage and the development of vaccines that use either killed whole-cells, which have more surface antigens, or proteins present in multiple serotypes.

Eradication of diseases

A cow with rinderpest in the "milk fever" position, 1982. The last confirmed case of rinderpest occurred in Kenya in 2001, and the disease was officially declared eradicated in 2011.

If herd immunity has been established and maintained in a population for a sufficient time, the disease is inevitably eliminated – no more endemic transmissions occur. If elimination is achieved worldwide and the number of cases is permanently reduced to zero, then a disease can be declared eradicated. Eradication can thus be considered the final effect or end-result of public health initiatives to control the spread of contagious disease. In cases in which herd immunity is compromised, on the contrary, disease outbreaks among the unvaccinated population are likely to occur.

The benefits of eradication include ending all morbidity and mortality caused by the disease, financial savings for individuals, health care providers, and governments, and enabling resources used to control the disease to be used elsewhere. To date, two diseases have been eradicated using herd immunity and vaccination: rinderpest and smallpox. Eradication efforts that rely on herd immunity are currently underway for poliomyelitis, though civil unrest and distrust of modern medicine have made this difficult. Mandatory vaccination may be beneficial to eradication efforts if not enough people choose to get vaccinated.

Free riding

Herd immunity is vulnerable to the free rider problem. Individuals who lack immunity, including those who choose not to vaccinate, free ride off the herd immunity created by those who are immune. As the number of free riders in a population increases, outbreaks of preventable diseases become more common and more severe due to loss of herd immunity. Individuals may choose to free ride or be hesitant to vaccinate for a variety of reasons, including the belief that vaccines are ineffective, or that the risks associated with vaccines are greater than those associated with infection, mistrust of vaccines or public health officials, bandwagoning or groupthinking, social norms or peer pressure, and religious beliefs. Certain individuals are more likely to choose not to receive vaccines if vaccination rates are high enough to convince a person that he or she may not need to be vaccinated, since a sufficient percentage of others are already immune.

Mechanism

Individuals who are immune to a disease act as a barrier in the spread of disease, slowing or preventing the transmission of disease to others. An individual's immunity can be acquired via a natural infection or through artificial means, such as vaccination. When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT) or herd immunity level (HIL), the disease may no longer persist in the population, ceasing to be endemic.

The theoretical basis for herd immunity generally assumes that vaccines induce solid immunity, that populations mix at random, that the pathogen does not evolve to evade the immune response, and that there is no non-human vector for the disease.

Theoretical basis

See also: Basic reproduction number

Further information: Mathematical modelling of infectious diseases

Graph of herd immunity threshold vs basic reproduction number with selected diseases

The critical value, or threshold, in a given population, is the point where the disease reaches an endemic steady state, which means that the infection level is neither growing nor declining exponentially. This threshold can be calculated from the effective reproduction number R_e, which is obtained by taking the product of the basic reproduction number R₀, the average number of new infections caused by each case in an entirely susceptible population that is homogeneous, or well-mixed, meaning each individual is equally likely to come into contact with any other susceptible individual in the population, and S, the proportion of the population who are susceptible to infection, and setting this product to be equal to 1:

${\displaystyle R_0\cdot S=1.}$

S can be rewritten as (1 − p), where p is the proportion of the population that is immune so that p + S equals one. Then, the equation can be rearranged to place p by itself as follows:

${\displaystyle R_0\cdot (1-p)=1,}$

${\displaystyle 1-p=\frac{1}{R_0},}$

${\displaystyle p_c=1-\frac{1}{R_0}.}$

With p being by itself on the left side of the equation, it can be renamed as p_c, representing the critical proportion of the population needed to be immune to stop the transmission of disease, which is the same as the "herd immunity threshold" HIT. R₀ functions as a measure of contagiousness, so low R₀ values are associated with lower HITs, whereas higher R₀s result in higher HITs. For example, the HIT for a disease with an R₀ of 2 is theoretically only 50%, whereas a disease with an R₀ of 10 the theoretical HIT is 90%.

When the effective reproduction number R_e of a contagious disease is reduced to and sustained below 1 new individual per infection, the number of cases occurring in the population gradually decreases until the disease has been eliminated. If a population is immune to a disease in excess of that disease's HIT, the number of cases reduces at a faster rate, outbreaks are even less likely to happen, and outbreaks that occur are smaller than they would be otherwise. If the effective reproduction number increases to above 1, then the disease is neither in a steady state nor decreasing in incidence, but is actively spreading through the population and infecting a larger number of people than usual.

An assumption in these calculations is that populations are homogeneous, or well-mixed, meaning that every individual is equally likely to come into contact with any other individual, when in reality populations are better described as social networks as individuals tend to cluster together, remaining in relatively close contact with a limited number of other individuals. In these networks, transmission only occurs between those who are geographically or physically close to one another. The shape and size of a network is likely to alter a disease's HIT, making incidence either more or less common.Mathematical models can use contact matrices to estimate the likelihood of encounters and thus transmission.

Values of R₀ and herd immunity thresholds (HITs) of contagious diseases prior to intervention

Disease	Transmission	R0	HIT
Measles	Aerosol	12–18	92–94%
Chickenpox (varicella)	Aerosol	10–12	90–92%
Mumps	Respiratory droplets	10–12	90–92%
COVID-19 (see values for specific strains below)	Respiratory droplets and aerosol	2.9-9.5	65–89%
Rubella	Respiratory droplets	6–7	83–86%
Polio	Fecal–oral route	5–7	80–86%
Pertussis	Respiratory droplets	5.5	82%
Smallpox	Respiratory droplets	3.5–6.0	71–83%
HIV/AIDS	Body fluids	2–5	50–80%
SARS	Respiratory droplets	2–4	50–75%
Diphtheria	Saliva	2.6 (1.7–4.3)	62% (41–77%)
Common cold (e.g., rhinovirus)	Respiratory droplets	2–3	50–67%
Mpox	Physical contact, body fluids, respiratory droplets, sexual (MSM)	2.1 (1.1–2.7)	53% (22–63%)
Ebola (2014 outbreak)	Body fluids	1.8 (1.4–1.8)	44% (31–44%)
Influenza (seasonal strains)	Respiratory droplets	1.3 (1.2–1.4)	23% (17–29%)
Andes hantavirus	Respiratory droplets and body fluids	1.2 (0.8–1.6)	16% (0–36%)
Nipah virus	Body fluids	0.5	0%
MERS	Respiratory droplets	0.5 (0.3–0.8)	0%

In heterogeneous populations, R₀ is considered to be a measure of the number of cases generated by a "typical" contagious person, which depends on how individuals within a network interact with each other. Interactions within networks are more common than between networks, in which case the most highly connected networks transmit disease more easily, resulting in a higher R₀ and a higher HIT than would be required in a less connected network. In networks that either opt not to become immune or are not immunized sufficiently, diseases may persist despite not existing in better-immunized networks.

Overshoot

The cumulative proportion of individuals who get infected during the course of a disease outbreak can exceed the HIT. This is because the HIT does not represent the point at which the disease stops spreading, but rather the point at which each infected person infects fewer than one additional person on average. When the HIT is reached, the number of additional infections does not immediately drop to zero. The excess of the cumulative proportion of infected individuals over the theoretical HIT is known as the overshoot.

Boosts

Further information: Artificial induction of immunity

Vaccination

Main articles: Vaccination and Vaccine

See also: Vaccine-preventable disease and List of human disease case fatality rates

The primary way to boost levels of immunity in a population is through vaccination. Vaccination is originally based on the observation that milkmaids exposed to cowpox were immune to smallpox, so the practice of inoculating people with the cowpox virus began as a way to prevent smallpox. Well-developed vaccines provide protection in a far safer way than natural infections, as vaccines generally do not cause the diseases they protect against and severe adverse effects are significantly less common than complications from natural infections.

The immune system does not distinguish between natural infections and vaccines, forming an active response to both, so immunity induced via vaccination is similar to what would have occurred from contracting and recovering from the disease. To achieve herd immunity through vaccination, vaccine manufacturers aim to produce vaccines with low failure rates, and policy makers aim to encourage their use. After the successful introduction and widespread use of a vaccine, sharp declines in the incidence of diseases it protects against can be observed, which decreases the number of hospitalizations and deaths caused by such diseases.

Assuming a vaccine is 100% effective, then the equation used for calculating the herd immunity threshold can be used for calculating the vaccination level needed to eliminate a disease, written as V_c. Vaccines are usually imperfect however, so the effectiveness, E, of a vaccine must be accounted for:

${\displaystyle V_c=\frac{1-\frac{1}{R_0}}{E}.}$

From this equation, it can be observed that if E is less than (1 − 1/R₀), then it is impossible to eliminate a disease, even if the entire population is vaccinated. Similarly, waning vaccine-induced immunity, as occurs with acellular pertussis vaccines, requires higher levels of booster vaccination to sustain herd immunity. If a disease has ceased to be endemic to a population, then natural infections no longer contribute to a reduction in the fraction of the population that is susceptible. Only vaccination contributes to this reduction. The relation between vaccine coverage and effectiveness and disease incidence can be shown by subtracting the product of the effectiveness of a vaccine and the proportion of the population that is vaccinated, p_v, from the herd immunity threshold equation as follows:

Measles vaccine coverage and reported measles cases in Eastern Mediterranean countries. As coverage increased, the number of cases decreased.

${\displaystyle \left(1-\frac{1}{R_0}\right)-(E\times p_v).}$

It can be observed from this equation that, all other things being equal ("ceteris paribus"), any increase in either vaccine coverage or vaccine effectiveness, including any increase in excess of a disease's HIT, further reduces the number of cases of a disease. The rate of decline in cases depends on a disease's R₀, with diseases with lower R₀ values experiencing sharper declines.

Vaccines usually have at least one contraindication for a specific population for medical reasons, but if both effectiveness and coverage are high enough then herd immunity can protect these individuals. Vaccine effectiveness is often, but not always, adversely affected by passive immunity, so additional doses are recommended for some vaccines while others are not administered until after an individual has lost his or her passive immunity.

Passive immunity

Main article: Passive immunity

Individual immunity can also be gained passively, when antibodies to a pathogen are transferred from one individual to another. This can occur naturally, whereby maternal antibodies, primarily immunoglobulin G antibodies, are transferred across the placenta and in colostrum to fetuses and newborns. Passive immunity can also be gained artificially, when a susceptible person is injected with antibodies from the serum or plasma of an immune person.

Protection generated from passive immunity is immediate, but wanes over the course of weeks to months, so any contribution to herd immunity is temporary. For diseases that are especially severe among fetuses and newborns, such as influenza and tetanus, pregnant women may be immunized in order to transfer antibodies to the child. In the same way, high-risk groups that are either more likely to experience infection, or are more likely to develop complications from infection, may receive antibody preparations to prevent these infections or to reduce the severity of symptoms.

Cost–benefit analysis

Herd immunity is often accounted for when conducting cost–benefit analyses of vaccination programs. It is regarded as a positive externality of high levels of immunity, producing an additional benefit of disease reduction that would not occur had no herd immunity been generated in the population. Therefore, herd immunity's inclusion in cost–benefit analyses results both in more favorable cost-effectiveness or cost–benefit ratios, and an increase in the number of disease cases averted by vaccination. Study designs done to estimate herd immunity's benefit include recording disease incidence in households with a vaccinated member, randomizing a population in a single geographic area to be vaccinated or not, and observing the incidence of disease before and after beginning a vaccination program. From these, it can be observed that disease incidence may decrease to a level beyond what can be predicted from direct protection alone, indicating that herd immunity contributed to the reduction. When serotype replacement is accounted for, it reduces the predicted benefits of vaccination.

History

Measles cases in the United States before and after mass vaccination against measles began.

Herd immunity was recognized as a naturally occurring phenomenon in the 1930s when it was observed that after a significant number of children had become immune to measles, the number of new infections temporarily decreased. Mass vaccination to induce herd immunity has since become common and proved successful in preventing the spread of many contagious diseases. Opposition to vaccination has posed a challenge to herd immunity, allowing preventable diseases to persist in or return to populations with inadequate vaccination rates.

The exact herd immunity threshold (HIT) varies depending on the basic reproduction number of the disease. An example of a disease with a high threshold was the measles, with a HIT exceeding 95%.

The term "herd immunity" was first used in 1894 by American veterinary scientist and then Chief of the Bureau of Animal Industry of the US Department of Agriculture Daniel Elmer Salmon to describe the healthy vitality and resistance to disease of well-fed herds of hogs. In 1916 veterinary scientists inside the same Bureau of Animal Industry used the term to refer to the immunity arising following recovery in cattle infected with brucellosis, also known as "contagious abortion." By 1923 it was being used by British bacteriologists to describe experimental epidemics with mice, experiments undertaken as part of efforts to model human epidemic disease. By the end of the 1920s the concept was used extensively - particularly among British scientists - to describe the build up of immunity in populations to diseases such as diphtheria, scarlet fever, and influenza. Herd immunity was recognized as a naturally occurring phenomenon in the 1930s when A. W. Hedrich published research on the epidemiology of measles in Baltimore, and took notice that after many children had become immune to measles, the number of new infections temporarily decreased, including among susceptible children. In spite of this knowledge, efforts to control and eliminate measles were unsuccessful until mass vaccination using the measles vaccine began in the 1960s. Mass vaccination, discussions of disease eradication, and cost–benefit analyses of vaccination subsequently prompted more widespread use of the term herd immunity. In the 1970s, the theorem used to calculate a disease's herd immunity threshold was developed. During the smallpox eradication campaign in the 1960s and 1970s, the practice of ring vaccination, to which herd immunity is integral, began as a way to immunize every person in a "ring" around an infected individual to prevent outbreaks from spreading.

Since the adoption of mass and ring vaccination, complexities and challenges to herd immunity have arisen. Modeling of the spread of contagious disease originally made a number of assumptions, namely that entire populations are susceptible and well-mixed, which is not the case in reality, so more precise equations have been developed. In recent decades, it has been recognized that the dominant strain of a microorganism in circulation may change due to herd immunity, either because of herd immunity acting as an evolutionary pressure or because herd immunity against one strain allowed another already-existing strain to spread. Emerging or ongoing fears and controversies about vaccination have reduced or eliminated herd immunity in certain communities, allowing preventable diseases to persist in or return to these communities.