This report summarizes a phase 3 clinical trial evaluating the safety and immunogenicity of RSVpreF in adults aged 18-59 years at high risk for severe respiratory syncytial virus (RSV) disease. Recognizing that older adults and immunocompromised individuals face heightened risks of severe RSV infection, the study aimed to assess whether the vaccine could provide effective protection in a younger high-risk population.
The trial enrolled 678 participants, randomized in a 2:1 ratio to receive either 120 µg of RSVpreF (n=453) or a placebo (n=225). Safety assessments focused on reactogenicity events and adverse events (AEs) within 7 days, as well as serious AEs (SAEs) and newly diagnosed chronic medical conditions (NDCMCs) throughout the study duration. The majority of reactogenicity events were mild or moderate, with severe events occurring in less than 2% of participants. Overall, AE frequencies were comparable between vaccine (7.1%) and placebo groups (7.6%), and no vaccine-related SAEs or NDCMCs were reported, indicating a favorable safety profile.
Immunogenicity was evaluated by measuring neutralizing antibody titers against RSV-A and RSV-B at one month post-vaccination. The immune responses in adults aged 18-59 were compared to those in a subset of participants aged 60 and older from a prior phase 3 trial (RENOIR), which demonstrated vaccine efficacy. The results met noninferiority criteria, with 95% confidence intervals for the ratios of neutralizing titers and seroresponse rates exceeding the predefined thresholds, confirming comparable immune responses across age groups.
In conclusion, RSVpreF was well tolerated in adults aged 18-59 at high risk for severe RSV disease and elicited robust immune responses similar to those seen in older adults where efficacy was previously established. These findings support the potential use of RSVpreF to prevent RSV-associated disease in younger high-risk populations.
Reference:
Davis M, Towner W, DeHaan E, Jiang Q, Li W, Rahman F, Patton M, Wyper H, Lino MM, Sarwar UN, Majid-Mahomed Z, Mehta S, Howitt W, Cannon K, Kalinina E, Cooper D, Swanson KA, Anderson AS, Gurtman A, Munjal I; MONeT Study Team. Bivalent RSVpreF Vaccine in Adults 18 to <60 Years Old With High-Risk Conditions. Clin Infect Dis. 2025 Apr 30;80(4):911-920. doi: 10.1093/cid/ciae550. PMID: 39523547; PMCID: PMC12043053
