The following is a summary of “Phase 1/2a Safety and Immunogenicity of an Adenovirus 26 Vector Respiratory Syncytial Virus (RSV) Vaccine Encoding Prefusion F in Adults 18–50 Years and RSV-Seropositive Children 12–24 Months,” published in the January 2023 issue of Infectious Diseases by Stuart, et al.

Despite no vaccine being authorized, respiratory syncytial virus (RSV) continued to be a major source of morbidity in children. For a study, researchers tested the Ad26.RSV.preF vaccine candidate’s safety and immunogenicity in both adults and kids.

Ad26.RSV.preF (1 × 1011 viral particles [vp] for adults, 5 × 1010 vp for children) or placebo, with 6-month immunogenicity and 1-year safety follow-up, were randomly assigned to 12 adults (18-50 years) and 36 RSV-seropositive children (12-24 months) in the randomized, double-blind, phase 1/2a, placebo-controlled study. An investigational result in children was respiratory syncytial virus infection.

No significant adverse events (AEs) were reported among the requested AEs in adults, mainly mild to moderate. Fever was detected in 14 (58.3%) of the Ad26.RSV.preF recipients were identified, but no significant adverse events (AEs) were linked to the vaccine in children. Pediatric geometric mean titers for RSV A2 neutralization at baseline rose from 121 (95% CI, 76-191) to 1,608 (95% CI, 730-3,544) on day 29, to 2,235 (95% CI, 1,586-3,150) at day 57, and remained high for 7 months. Children receiving Ad26.RSV.preF (1, 4.2%) had lower respiratory syncytial virus infection rates than children receiving a placebo (5, 41.7%).

Ad26.RSV.preF showed immunogenicity in young children and healthy adults, with no safety issues noted. Children who tested negative for RSV were evaluated.