Phase 1/2a Safety and Immunogenicity of an Adenovirus 26 Vector RSV Vaccine Encoding Prefusion F in Adults 18-50 Years and RSV Seropositive Children 12-24 Months.
Stuart A., Virta M., Williams K., Seppa I., Hartvickson R., Greenland M., Omoruyi E., Bastian AR., Haazen W., Salisch N., Gymnopoulou E., Callendret B., Faust SN., Snape MD., Heijnen E.
BACKGROUND: Respiratory syncytial virus (RSV) remains a leading cause of pediatric morbidity, with no approved vaccine. We assessed the safety and immunogenicity of the Ad26.RSV.preF vaccine candidate in adults and children. METHODS: In this randomized, double-blind, phase 1/2a, placebo-controlled study, 12 adults (18-50 years) and 36 RSV-seropositive children (12-24 months) were randomized 2:1 to Ad26.RSV.preF (1 × 1011 viral particles [vp] for adults, 5 × 1010 vp for children) or placebo, at day 1 and 29, with 6-month immunogenicity and 1-year safety follow-up. RSV infection was an exploratory outcome in children. RESULTS: In adults, solicited adverse events (AEs) were generally mild-moderate, with no serious AEs. In children, no vaccination-related serious AEs were reported; fever was reported in 14 (58.3%) Ad26.RSV.preF recipients. Baseline pediatric geometric mean titers for RSV A2 neutralization increased from 121 (95% confidence interval [CI], 76-191) to 1608 (95% CI, 730-3544) at day 29, and 2235 (95% CI, 1586-3150) at day 57, remaining elevated over 7 months. RSV infection was confirmed in fewer children receiving Ad26.RSV.preF (1, 4.2%) than placebo (5, 41.7%). CONCLUSIONS: Ad26.RSV.preF demonstrated immunogenicity in healthy adults and toddlers, with no safety concerns raised. Evaluations in RSV-seronegative children are underway.