The following is a summary of “Long-term efficacy and immunogenicity of Ad26.RSV.preF–RSV preF protein vaccine (CYPRESS): a randomised, double-blind, placebo-controlled, phase 2b study,” published in the May 2024 issue of Infectious Disease by Falsey et al.
While existing respiratory syncytial virus (RSV) vaccines offer protection within a single season, Ad26.RSV.preF protein demonstrated promising 80% efficacy against RSV lower respiratory tract disease (LRTD) in older adults for one season.
Researchers conducted a retrospective study determining the single-season efficacy of Ad26.RSV.preF-RSV preF protein could be sustained over 3 RSV seasons.
They conducted a phase 2b, double-masked, placebo-controlled study (CYPRESS) at 40 US centers randomly assigned adults 65 years or older (1:1) to receive either the Ad26.RSV.preF–RSV preF protein vaccine or a placebo injection. Neither participants nor researchers knew who received the vaccine until the study was complete and the primary endpoint, RSV-mediated LRTD was previously reported. The vaccine efficacy against RSV-positive LRTD in seasons 2 and 3 per-protocol efficacy set was evaluated. Additionally, participants were assessed for humoral and cellular immune responses to the vaccine. Safety data (previously reported for the season was collected through study completion, including SAEs related to the vaccine.
The result showed that 6,672 adults were screened, and only 5,782 were enrolled and vaccinated (August to November 13, 2019), with 2,891 receiving the vaccine and an equal number receiving a placebo. The per-protocol efficacy analysis for season 2 included 2,124 vaccine recipients and 2,126 placebo recipients, while for season 3, involving 864 and 881 participants, 2,795 vaccine recipients and 2,803 placebo recipients were analyzed. Vaccine efficacy against RSV LRTD was found to be 76.1% (95% CI 26.9–94.2) for seasons 2 and 3 combined and 78.7% (57.3–90.4) across all 3 seasons. In the immunogenicity subset (vaccine n=97; placebo n=98), immune responses persisted above baseline levels for at least one year. The SAEs were reported in 47 (2·1%) of vaccine recipients and 45 (2·1%) of placebo recipients during season 2 and in 12 (1·3%) of vaccine recipients and 10 (1·1%) of placebo recipients during season 3 with no severe or fatal AEs.
Investigators found that over three seasons in older adults, the Ad26.RSV.preF-RSV preF vaccine consistently showed strong efficacy against RSV LRTD.
Source: thelancet.com/journals/laninf/article/PIIS1473-3099(24)00226-3/abstract#%20