Safety and Tolerability of an Ad26.RSV.preF-based Vaccine in a Phase 2b Study in Older Adults

Abstract Respiratory syncytial virus (RSV) may cause severe lower respiratory tract disease in older adults and there is currently no approved vaccine. We assessed the safety and reactogenicity of an Ad26.RSV.preF-based vaccine in a randomized, double-blind, placebo-controlled Phase 2b proof-of-concept trial in adults aged ≥65 years (CYPRESS; NCT03982199). Prior to the RSV season, participants were randomized 1:1 to receive an Ad26.RSV.preF-based vaccine or placebo. Solicited adverse events (AEs; fatigue, headache, nausea, myalgia, fever, injection site reactions) and unsolicited AEs were assessed from time of vaccination to Day 8 and Day 29, respectively, in a safety subset of 695 participants (vaccine, n=348; placebo, n=347). All participants were followed for serious AEs (SAEs) until the end of the RSV season or 6 months after vaccination, whichever occurred later. A total of 5728 participants were randomized and received vaccine or placebo (n=2891 in each group). In the safety subset, the frequency of solicited AEs and Grade ≥3 solicited AEs was 51.4% and 3.2% in the vaccine group and 20.2% and 0.6% in the placebo group, respectively. The most frequent solicited AEs in the vaccine group were fatigue, myalgia, headache, and injection site pain/tenderness. The rates of unsolicited AEs and Grade ≥3 unsolicited AEs were similar between the vaccine (16.7% and 1.7%) and placebo (14.4% and 1.4%) groups. In the overall study population, the rate of SAEs was similar between groups (vaccine, 4.6%; placebo, 4.7%); none were considered related to the vaccine. The Ad26.RSV.preF-based vaccine was safe and well tolerated in adults aged ≥65 years.