Positivity rates of COVID-19 are not an indication of herd immunity. The rate of positivity in a community is defined as the percentage of total COVID-19 tests that come back positive out of all the people who have been tested in that community or population, within a given time period. Positivity rates can indicate an increasing outbreak, if the rate of positive tests increases while the amount of testing stays the same. A positivity rate can also indicate that not enough tests are being conducted, if more tests come back with positive results but tests were conducted on a smaller percentage of the population than the week before. Neither of these have anything to do with herd immunity.

"Herd immunity" refers to a given percentage of people that need to become immunized to a virus, through vaccines or through becoming infected in a natural setting, against a virus in order to provide safety for an entire population—i.e. the herd. It's the idea that if most people are immune, then the rate of transmission will be low or non-existent. COVID-19 is not vaccine-preventable at this time and we know very little about how we become immune to the virus. Herd immunity would require a large majority of the population to become infected with the virus and obtain long-term immunity to COVID-19 — but since we know so little about long-term immunity right now, we can't say anything about herd immunity in relation to COVID-19.

Percent positive rates of COVID-19 are not being used to determine herd immunity in a community because we know so little about immunity in general, and because positive rates can mean a wide variety of things. If there is a higher percentage of positive test results in a region, this is not indicative of any potential for herd immunity, because evidence to support long-term immunity is lacking.

A Facebook post from August 4, 2020, falsely claimed that the current national positivity rate demonstrates that herd immunity has been reached for COVID-19. The post attempted to analyze a positivity rate graph from Johns Hopkins, but also included the author's own insights about testing, population level risk assessments, and added in 'bumps' to describe what he assumed were increases in testing. Though the post noted that the author believed an increase in positivity rates were being reported for political reasons (extending the shutdowns and requiring continued mask use) there is no evidence to support this claim. Additionally, there is no evidence to support claims that we've reached herd immunity, that COVID-19 positivity rates indicate anything about a population's immunity, or that 60% of a population needs to be infected in order to reach herd immunity for the virus.

On October 4, 2020, a proposal called the Great Barrington Declaration was signed in Great Barrington, Massachusetts, recommending the end of stay-at-home orders for people perceived to be at lower risk for COVID-19 until herd immunity is developed. One of President Trump's science advisors is a lead author behind the Great Barrington Declaration, which was funded by the libertarian think tank called the American Institute for Economic Research that is behind other statements to allow sweatshop labor and reduce environmental protections. The Great Barrington Declaration has since been embraced by several White House officials, while numerous public health agencies including the World Health Organization (WHO) have responded with warnings. An open letter by the American Public Health Association and 13 other public health organizations in the U.S. warned that the Great Barrington Declaration "is not a strategy, it is a political statement. It ignores sound public health expertise. It preys on a frustrated populace. Instead of selling false hope that will predictably backfire, we must focus on how to manage this pandemic in a safe, responsible, and equitable way." Over 4,800 scientists, researchers and healthcare professionals have signed another response published in the Lancet on October 14, 2020 called the John Snow Memorandum, which condemns the policies recommended by the Great Barrington Declaration and calls for acting based on evidence.

Outside of the U.S., other politicians have tried to promote achieving herd immunity as a pandemic response approach. For example, Sweden's policies had mostly avoided preventative public health measures like lockdowns and mask wearing, but newer policies starting October 19, 2020 are more restrictive in response to Sweden seeing one of the highest per-capita death rates in the world (58.6 per 100,000 people) and an average increase in daily COVID-19 cases by 173% since the autumn of 2020. While some Swedish politicians have tried to avoid publicly using the language of herd immunity, journalists have obtained emails between high-level Swedish public health officials revealing that achieving herd immunity was discussed as a strategy as early as March 2020. In the U.K., Prime Minister Boris Johnson's chief scientific adviser said on March 13 that he believed their country would be able to achieve herd immunity, but the U.K. ultimately changed its strategy and did impose a lockdown after medical experts warned that attempting to achieve herd immunity could risk killing hundreds of thousands of people. In Brazil, researchers have been studying the city of Manaus, where it is estimated that 44% to 66% of the population was infected with COVID-19 in the summer of 2020 and cases had started to drop, only to start rising again in the fall of 2020. While some suggested that Manaus may have reached herd immunity, others are warning that cases are still rising in Manaus and more lives should not be put at risk.