Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) significantly impact the health of older adults globally. Researchers recently presented promising results for VXB-241, a bivalent RSV hMPV vaccine candidate, in a Phase 1 clinical trial. This study evaluates the safety and immunogenicity of this unadjuvanted liquid formulation designed to simplify vaccination schedules.

The ongoing randomised trial involved older adults aged 60 to 83 years. Participants received varying doses of VXB-241, ranging from 60 μg to 480 μg. Investigators compared these groups against a placebo and the licensed AS01-adjuvanted RSV vaccine. Specifically, the interim analysis focused on safety and antibody responses one month after injection.

Immunogenicity of the Bivalent RSV hMPV Vaccine

Data showed that VXB-241 induced robust neutralising antibody titres against RSV-A, RSV-B, hMPV-A, and hMPV-B. Furthermore, the 240 μg dose level yielded geometric mean fold increases that compared favourably with the active control. For instance, RSV-A and RSV-B responses were at least as high as those seen with the licensed adjuvanted vaccine. Additionally, VXB-241 elicited strong responses against hMPV, whereas the active control showed negligible effects against this virus.

Regarding safety, the candidate vaccine displayed a clinically acceptable profile. While solicited adverse events occurred more frequently in the vaccine groups than in the placebo group, most reactions were mild and transient. Moreover, no safety signals emerged during this interim analysis. Consequently, these findings support the continued clinical development of VXB-241 as a potential tool for protecting older populations.

Frequently Asked Questions

What is VXB-241 and how does it work?

VXB-241 is a bivalent vaccine candidate that targets both RSV and hMPV. It utilizes a recombinant glycoprotein F-molecular clamp technology to stabilise viral antigens in their pre-fusion state, which enhances the immune response.

Is the bivalent RSV hMPV vaccine safe for the elderly?

Yes, the 1-month interim analysis of the Phase 1 trial reported a clinically acceptable safety and reactogenicity profile. Most adverse events were mild and no significant safety signals emerged among the older adult participants during the study period.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition or vaccination. Refer to the latest local and national guidelines for clinical practice.

References

Della Cioppa G et al. Safety, immunogenicity, and dose ranging of a bivalent respiratory syncytial virus and human metapneumovirus glycoprotein F-molecular clamp vaccine candidate in older adults: 1-month interim analysis of an ongoing randomised, observer-blind, placebo- and active-controlled, phase 1 trial. Vaccine. 2026 Jun 01. doi: undefined. PMID: 42224773.

ClinicalTrials.gov. A Study of RSV-HMPV Bivalent Vaccine VXB-241 in Older Adults. NCT06556147.

Vicebio Ltd. Vicebio Advances Clinical Study of RSV/hMPV Bivalent Vaccine. PR Newswire. November 21, 2024.