J&J's one-shot COVID vaccine is safe and generates promising immune response in early trial

J&J scientists randomly assigned healthy adults between the ages of 18 and 55 and those 65 and older to receive a high or low dose of its vaccine — called Ad26.COV2.S — or a placebo. Most of the volunteers produced detectable neutralizing antibodies, which researchers believe play an important role in defending cells against the virus, after 28 days, according to the trial data. By day 57, all volunteers had detectable antibodies, regardless of vaccine dose or age group, and remained stable for at least 71 days in the 18-to-55 age group.