A Novel Influenza A (H1N1) Vaccine in Various Age Groups

Background There is an urgent need for a vaccine that is effective against the 2009 pandemic influenza A (H1N1) virus. Methods A split-virus, inactivated candidate vaccine against the 2009 H1N1 virus was manufactured, and we evaluated its safety and immunogenicity in a randomized clinical trial. Subjects were between 3 and 77 years of age, stratified into four age groups. The immunization schedule consisted of two vaccinations, 21 days apart. Subjects were injected with placebo or with vaccine, with or without alum adjuvant, at doses of 7.5 μg, 15 μg, or 30 μg. Serologic analysis was performed at baseline and on days 21 and 35. Results A total of 2200 subjects received one dose, and 2103 (95.6%) received the second dose, of vaccine or placebo. No severe adverse side effects associated with the vaccine were noted. In the nonadjuvanted-vaccine groups, injection-site or systemic reactions, most mild in nature, were noted in 5.5 to 15.9% of subjects. Among the subjects receiving 15 μg of nonadjuvanted vaccine...