The following is a summary of “Safety and Immunogenicity of a Respiratory Syncytial Virus Prefusion F (RSVPreF3) Candidate Vaccine in Older Adults: Phase 1/2 Randomized Clinical Trial,” published in the March 2023 issue of Infectious Diseases by Roels, et al.

For a study, researchers sought to assess the safety and effectiveness of RSVPreF3 vaccine formulations containing the stabilized prefusion conformation of respiratory syncytial virus (RSV) fusion protein (RSVPreF3) in young and older adults. 

The study enrolled 48 young adults (YAs; aged 18–40 years) and 1,005 older adults (OAs; aged 60–80 years) between January and August 2019. The participants were randomly allocated to receive either two doses of unadjuvanted (YAs and OAs) or AS01-adjuvanted (OAs) vaccines or placebo, administered two months apart, with safety and immunogenicity monitored up to one month (YAs) or twelve months (OAs) after the second vaccination.

The RSVPreF3 vaccines produced humoral (RSVPreF3-specific immunoglobulin G [IgG] and RSV-A neutralizing antibody) responses, which increased depending on the amount of the antigen and peaked after dose 1. At each dosage, geometric mean frequencies of polyfunctional CD4⁺ T cells increased compared to prevaccination and were substantially higher in adjuvanted vaccine recipients than in unadjuvanted recipients. Until the end of the follow-up period, postvaccination immunological responses persisted. The majority of the unintended negative outcomes were mild to moderate and brief. None of the evaluated formulations had any safety issues, despite the greater reactogenicity reported in vaccines containing AS01.

Based on the safety and immunogenicity profiles, the AS01E-adjuvanted vaccine containing 120 μg of RSVPreF3 was chosen for further clinical development.

Reference: academic.oup.com/jid/article/227/6/761/6651941