Johnson & Johnson’s one-dose coronavirus vaccine is safe and appears to generate a promising immune response in both young and elderly volunteers, according to trial data published Wednesday in the New England Journal of Medicine. 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. Some participants in the 18-to-55 age group were also selected to receive a second dose of the vaccine.
