A rumor that circulation of #COVID19 in California in fall 2019 has resulted in herd immunity. This is empirically not the case.
There is a lot of Twitter chatter surrounding a rumor that circulation of #COVID19 in California in fall 2019 has resulted in herd immunity. This is empirically not the case. COVID-19 was first introduced into the USA in Jan/Feb 2020. 1/18
— Trevor Bedford (@trvrb) April 12, 2020