Widescale SARS-CoV-2 vaccines are soon expected to be administered in the United States under FDA approved Emergency Use Authorizations. If and when a sufficient number of people receive these vaccines, in combination with immunity provided through naturally occurring antibodies among those previously infected, the population is expected to reach herd immunity.
Current research suggests that herd immunity for COVID-19 is expected when 60-70% of a population is immune to the virus, either through vaccination or past infection.
Early research results also suggest that SARS-CoV-2 immunity is long-lasting and may be consistent with the long term immunity observed in SARS.
On November 22nd, Dr. Slaoui, leader of Operation Warp Speed, stated that he expects herd immunity to likely be achieved in May 2021.
70% or so of the population being immunized would allow for true herd immunity to take place, that is likely to happen somewhere in the month of May, or something like that based on our plans. Dr. Slaoui, November 22nd, 2020
However, vaccine hestitancy may be high, with 42% of Americans in late October 2020 saying they would be unwilling to take a SARS-CoV-2.
When will the United States reach herd immunity (>230M) for COVID-19?
This question resolves as the date when the first reliable media report is published that states that >230M of the US population (~70%) have either received a SARS-CoV-2 vaccine or has been previously been infected by the virus.
While this question is intended as an operationalization of "herd immunity", because herd immunity is difficult to ascertain, the resolution criteria is not herd immunity itself, but rather reaching 230M (~70%) either vaccinated or having been previously infected, as a proxy indicator.
If this does not resolve before 31 December 2022, it resolves as >31 December 2022.