(August 19, 2021)

In March 2021, when Americans first began hearing about the Delta variant of Covid-19, breakthrough infections among fully-vaccinated Angelenos accounted for just 2% of that month’s case total. By June, when Delta accounted for 50% of all variants in Los Angeles, breakthrough infections among fully-vaccinated residents had risen to 20% of all identified cases. In late July, county officials reported that the Delta variant had overwhelmed all others, accounting for more than 90% of all positive tests analyzed for variants. As a result, the ratio of breakthrough cases increased to 30%, local health officials announced today.