Respiratory syncytial virus (RSV) poses a serious health threat, particularly for older adults and individuals with underlying chronic conditions. Each year, RSV contributes to thousands of deaths, highlighting the need for effective preventative measures. Pfizer’s Abrysvo vaccine, already approved for individuals 60 years and older and infants, is now showing promising results in a phase 3 clinical trial (MONeT, NCT05842967) for adults aged 18 to 59 at increased risk of severe RSV-associated lower respiratory tract disease (LRTD).
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RSV can severely impact the lungs and airways, leading to serious infections. Two subgroups of the virus, RSV-A and RSV-B, circulate seasonally, further complicating prevention efforts.
The MONeT Clinical Trial: Investigating Abrysvo’s Efficacy and Safety
The MONeT trial aimed to evaluate the safety, tolerability, and immunogenicity of a single dose of Abrysvo in adults at heightened risk for RSV-LRTD. The study included two substudies: substudy A focused on individuals aged 18 to 59 with chronic medical conditions, while substudy B enrolled immunocompromised individuals aged 18 to 60 and older.
Healthcare workers administering a vaccine
Study Design and Participants
Substudy A enrolled 681 participants with chronic conditions like asthma, diabetes, or chronic obstructive pulmonary disease (COPD), randomly assigning them to receive either Abrysvo or a placebo. Substudy B included 200 immunocompromised participants who received two doses of Abrysvo approximately one month apart.
Promising Results: Safety and Immunogenicity
The trial results indicate that Abrysvo was well-tolerated and safe in both substudies, meeting the primary safety endpoint. Importantly, the vaccine also met the co-primary endpoint of immunogenicity, demonstrating a significant increase in neutralizing antibody responses against both RSV-A and RSV-B. One month after vaccination, participants showed a 4-fold increase in serum neutralizing titers, suggesting a robust immune response. These findings align with previous phase 3 studies of Abrysvo, further reinforcing the vaccine’s potential.
Implications for RSV Prevention in At-Risk Adults
The MONeT study is particularly significant because it addresses a critical unmet need: protecting adults aged 18 to 59 with underlying health conditions from severe RSV infections. Currently, no RSV vaccine is approved for this age group, despite the fact that a substantial portion of this population faces increased risk. For instance, in the United States, approximately 9.5% of individuals aged 18 to 49 and 24.3% of individuals aged 50 to 64 have chronic conditions that elevate their risk of RSV-associated LRTD.
Future Directions and Potential Impact
Pending regulatory approval, Abrysvo could become the first and only RSV vaccine available for adults aged 18 and older, offering much-needed protection against this potentially life-threatening virus. The positive results from the MONeT trial represent a crucial step toward achieving this goal and underscore the potential of Abrysvo to significantly reduce the burden of RSV-related illness in vulnerable populations.
Conclusion: A Significant Advance in RSV Prevention
The MONeT trial results provide compelling evidence supporting the efficacy and safety of Abrysvo in protecting at-risk adults from RSV-associated LRTD. This vaccine has the potential to revolutionize RSV prevention, offering hope to millions of individuals who are currently vulnerable to severe RSV infections. For personalized treatment plans and guidance on RSV prevention, consult with a healthcare professional.
References
Pfizer. Pfizer Announces Positive Top-Line Results from Phase 3 Study of ABRYSVO® in Adults Aged 18 to 59 at Increased Risk for RSV Disease. News release. April 9, 2024. Accessed April 17, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-results-phase-3-study-1.
