Real–World Data Show Efficacy of Beyfortus Against Hospitalization for RSV-Associated Bronchiolitis
Study findings suggest that campaigns starting each year at the beginning of respiratory syncytial virus outbreaks, instead of continuous treatment of newborns throughout the year, may improve the usefulness of the Beyfortus program.
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An observational study (NCT06030505) in a real-world setting found that Beyfortus (nirsevimab) lowers the risk of hospitalized respiratory syncytial virus (RSV)-associated bronchiolitis in infants younger than 12 months of age.1,2
The FDA approved Beyfortus in July 2023 for neonates and infants born during or entering their first RSV season, and for children up to 2 years of age with vulnerability to severe RSV disease through their second RSV season. The monoclonal antibody has previously been found to protect against RSV-associated lower respiratory tract disease in newborns and infants under 8 months of age born during or entering their first RSV season.3
The authors of the current study, published in The New England Journal of Medicine, noted that the efficacy of Beyfortus in their research appeared to be slightly higher than what was found in the MEDLEY and MELODY trials, but similar to findings from the HARMONIE trial.
“Given that the protection conferred by [Beyfortus] may decrease over time, this situation may have contributed to the higher effectiveness found in our study than in the MEDLEY and MELODY trials,” the study authors wrote. “Overall, these findings suggest that campaigns that start each year at the beginning of the RSV outbreak, as is done for influenza, rather than continuous treatment of newborns throughout the year, may improve the usefulness of the [Beyfortus] program.”1
The prospective, multicenter, matched case–control study evaluated the efficacy of Beyfortus on hospitalization for RSV-associated bronchiolitis among 1035 infants under 12 months of age who were hospitalized for RSV-associated bronchiolitis between October 15 and December 10, 2023. Infants with clinical visits to the same hospitals for conditions unrelated to RSV infection were used as the control group, with case patients matched in a 2:1 ratio based on age, date of hospital visit, and study center. The study’s primary outcome was the efficacy of Beyfortus against hospitalization for RSV-associated bronchiolitis by means of a multivariate conditional logistic-regression model with adjustment for confounders.
Among the total study population, 690 were case patients with a median age of 3.1 months (interquartile range, 1.8 to 5.3) and 345 were matched control patients with a median age of 3.4 months (interquartile range, 1.6 to 5.6). In the total population, 60 case patients and 97 control patients were previously administered Beyfortus. The vaccine’s estimated adjusted efficacy against hospitalization for RSV-associated bronchiolitis was 83.0% (95% confidence interval [CI], 73.4 to 89.2), with sensitivity analyses showing similar findings to the primary analysis.
The efficacy of Beyfortus against RSV-associated bronchiolitis resulting in critical care was 69.6% (95% CI, 42.9 to 83.8), with 27 of 193 case patients (14.0%) compared to 47 of 146 matched control patients (32.2%). The vaccine’s efficacy against RSV-associated bronchiolitis resulting in ventilatory support was 67.2% (95% CI, 38.6 to 82.5), with 27 of 189 case patients (14.3%) compared to 46 of 151 matched control patients (30.5%).
“In this real-world study, we estimated the postlicensure effectiveness of [Beyfortus] therapy against hospitalization for RSV-associated bronchiolitis among infants younger than 12 months of age and found an overall effectiveness of 83.0%,” the study authors wrote. “This level of effectiveness was consistent across age groups. In addition, [Beyfortus] therapy was effective against the most severe forms of RSV-associated bronchiolitis—those leading to PICU admission and ventilatory support.”1
References
1. Assad Z., et al. Nirsevimab and Hospitalization for RSV Bronchiolitis. N Engl J Med 2024;391:144-154. DOI: 10.1056/NEJMoa2314885. Vol. 391 No. 2.
2. Effectiveness of Nirsevimab in Children Hospitalised With RSV Bronchiolitis (ENVIE). ClinicalTrials.gov. April 19, 2024. Accessed July 11, 2024. https://clinicaltrials.gov/study/NCT06030505
3. Limited Availability of Nirsevimab in the United States—Interim CDC Recommendations to Protect Infants from Respiratory Syncytial Virus (RSV) during the 2023–2024 Respiratory Virus Season. US Centers for Disease Control and Prevention. News release. October 24, 2023. Accessed July 11, 2024. https://emergency.cdc.gov/han/2023/han00499.asp
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