RSV vaccine is safe and effective in adults 60 years and older, but the absolute risk reduction is small

Reference

Walsh EE, Pérez Marc G, Zareba AM, et al, for the RENOIR Clinical Trial Group. Efficacy and safety of a bivalent RSV prefusion F vaccine in older adults. N Engl J Med 2023;388(16):1465-1477.

Synopsis

RSV infection causes the most problems in the very young and the very old. Another study in the same issue of this journal reported on a successful trial of a novel RSV vaccine in pregnant women to protect their offspring. This study identified 34,284 adults 60 years and older who were healthy or who had stable chronic comorbidities and randomized them to receive the RSV vaccine (120 mcg) or matching placebo injection. At baseline, the patients' mean age was 68 years, 38% were 70 years or older, and 22% were non-White. Participants came from 7 countries; 60% were from the United States. Approximately half of the patients had at least one high risk condition like heart, liver, renal, or lung disease. Analysis of the primary outcome only included patients who had received the assigned injection and were followed up for at least 15 days. Participants were followed up for a mean of 7 months after injection. The likelihood of any RSV infection was significantly lower in the vaccine group (0.13% vs 0.34%; number needed to treat [NNT] = 472), as was RSV infection with 2 or more symptoms (0.065% vs 0.19%; NNT = 773) and RSV infection with 3 or more symptoms (0.012% vs 0.082%; NNT = 1416). Only 25% of patients with 2 or more symptoms had shortness of breath, and only approximately 10% had tachypnea. Local reactions were reported by 12% of those who received the vaccine and by 7% of those who received the placebo. Otherwise, there were no differences in safety outcomes between the groups, with only 3 severe reactions attributed to the vaccine (including 2 patients with Guillain-Barré syndrome) in more than 17,000 vaccinated participants. According to the investigators, there were too few cases of illness requiring hospitalization or oxygenation to report.