Efficacy of the AZD1222 (ChAdOx1 nCoV-19) COVID-19 Vaccine Against SARS-CoV-2 Variants of Concern

In this South African phase 1/2b study, we demonstrated vaccine efficacy (VE) of two doses of AZD1222 for asymptomatic and symptomatic SARS-CoV-2 infection: 90.6% against wild-type and 77.1% against the Delta variant ≥9 months after vaccination. VE against infection with the Beta variant, which preceded circulation of Delta, was 6.7%. Clinical trial identifier CT.gov NCT04444674