Vaccine Protects Against RSV-Mediated Lower Respiratory Tract Disease in Older Adults

In a proof-of-concept trial in older adults, a respiratory syncytial virus (RSV) vaccine demonstrated an efficacy between 70% and 80%, depending on the definition of RSV-mediated lower respiratory tract disease used. Researchers published the findings in The New England Journal of Medicine. 

“RSV can cause serious lower respiratory tract disease in older adults, but no licensed RSV vaccine currently exists,” researchers explained in the study background. “An adenovirus serotype 26 RSV vector encoding a prefusion F (preF) protein (Ad26.RSV.preF) in combination with RSV preF protein was previously shown to elicit humoral and cellular immunogenicity.”

The double-blind, phase 2b trial, which was funded by Janssen Vaccines and Prevention, included 5782 adults ages 65 or older. Participants were randomly assigned to receive the Ad26.RSV.preF–RSV preF protein vaccine or placebo. 

The study’s primary end point was the first occurrence of RSV-mediated lower respiratory tract disease, which researchers defined in three ways. Definition 1 was at least three symptoms of lower respiratory tract infection. Definition 2 was at least two symptoms of lower respiratory tract infection. Definition 3 was at least two symptoms of lower respiratory tract infection or at least one symptom of lower respiratory tract infection plus at least one systemic symptom.

Cases meeting definition 1 occurred in 6 vaccine recipients and 30 placebo recipients; definition 2, in 10 vaccine recipients and 40 placebo recipients; and definition 3, in 13 vaccine recipients and 43 placebo recipients, according to the study. 

Vaccine efficacy was 80% for cases meeting definition 1, 75% for definition 2, and 69.8% for definition 3, researchers reported. Between baseline and day 15, RSV A2 neutralizing antibody titers increased by a factor of 12.1 with vaccination.

Local and systemic adverse events were more common in participants who received the vaccine, and most were mild to moderate in severity, the study found. The frequency of serious adverse events was 4.6% in the vaccine group and 4.7% in the placebo group.

“In adults 65 years of age or older, Ad26.RSV.preF–RSV preF protein vaccine was immunogenic and prevented RSV-mediated lower respiratory tract disease,” researchers concluded.

Reference:
Falsey AR, Williams K, Gymnopoulou E, et al. Efficacy and safety of an Ad26.RSV.preF-RSV preF protein vaccine in older adults. N Engl J Med. 2023;388(7):609-620. doi: 10.1056/NEJMoa2207566