On Sept. 15, 2021, Moderna announced new analysis suggesting that the COVID-19 vaccine was highly effective against circulating variants of concern, including in a vaccine effectiveness study conducted in partnership with Kaiser Permanente Southern California and in a separate recent publication by the U.S. Centers for Disease Control and Prevention.

In a prospective cohort study at Kaiser Permanente Southern California (KPSC), an analysis of 352,878 recipients of 2 doses of mRNA-1273 matched to 352,878 unvaccinated individuals found a vaccine effectiveness of 87% (99.3% CI: 85-90%) against COVID-19 diagnosis and 96% (99.3% CI: 91-98%) against COVID-19 hospitalization. The study was conducted during the emergence of the Delta variant, which was identified in 47% of cases in fully vaccinated individuals. These data were posted to a preprint server and submitted for peer review.