Falsey AR, Sobieszczyk ME, Hirsch I, et al. - In this ongoing, double-blind, randomized, placebo-controlled, phase 3 clinical trial, AZD1222(ChAdOx1 nCoV-19) was identified as safe and efficacious in averting symptomatic and severe Covid-19 across diverse populations that included older adults.

• There were a total of 32,451 participants who received either AZD1222 (21,635 participants) or placebo (10,816 participants).

• In the AZD1222 group, incidences of serious and medically attended adverse events and adverse events of special interest were low and were similar to those observed in the placebo group, indicating AZD1222 as safe.

• Both groups generally had mild or moderate solicited local and systemic reactions.

• As per estimates, the overall vaccine efficacy was 74.0% and in participants 65 years of age or older, the vaccine efficacy was 83.5%.

• Across a range of demographic subgroups, consistently high vaccine efficacy was noted.

• There appeared no severe or critical symptomatic Covid-19 cases among the 17,662 participants in the AZD1222 group in the fully vaccinated analysis subgroup; whereas the placebo group had 8 cases among the 8,550 participants.

• For preventing SARS-CoV-2 infection, the estimated vaccine efficacy (nucleocapsid antibody seroconversion) was 64.3%.

• Increase in SARS-CoV-2 spike protein binding and neutralizing antibodies occurred after the first dose and their further increase was observed when measured 28 days after the second dose.