Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19

Trial (n=39,321) found single dose of Ad26.COV2.S vaccine protected against moderate-severe–critical Covid-19 with onset ≥14 days after administration (116 cases vaccine vs. 348 placebo; efficacy, 66.9%) and ≥28 days after administration (66 vs. 193 cases; efficacy, 66.1%).

New England Journal of Medicine