Comparative Efficacy of Nirsevimab versus Palivizumab for the Prophylaxis of Respiratory Syncytial Virus Bronchiolitis: A Meta-Analysis

Abstract

Respiratory syncytial virus (RSV) remains the leading cause of lower respiratory tract infections in infants and children, imposing a substantial burden on healthcare systems and families. Passive immunization with monoclonal antibodies is a key preventive strategy, evolving from the monthly palivizumab regimen to the recently introduced single-dose nirsevimab with an optimized pharmacological profile. Although both agents have demonstrated efficacy versus placebo, direct comparative effectiveness on clinically relevant outcomes, such as bronchiolitis, remains unclear due to the absence of head-to-head randomized trials. This systematic review and meta-analysis aimed to compare the effectiveness of nirsevimab and palivizumab in preventing RSV bronchiolitis in pediatric populations. Comprehensive searches were conducted in ScienceDirect, Google Scholar, MEDLINE, and SciELO without language or date restrictions. Eleven studies, totaling 31,928 patients, met inclusion criteria. Data on study design, participant characteristics, intervention regimens, outcomes, and risk of bias were extracted and analyzed using a random-effects model with logit transformation to stabilize extreme proportions. Heterogeneity was quantified using I², and publication bias was assessed via Egger’s test. Pooled analysis showed a significantly higher incidence of RSV bronchiolitis in the nirsevimab group (0.231; 95% CI 0.126–0.387) compared with the palivizumab group (0.038; 95% CI 0.020–0.072), corresponding to an absolute risk difference of 0.193 and a number needed to treat (NNT) of 6. Despite high heterogeneity (I²=96.4%), the results remained statistically robust. The superior efficacy of palivizumab likely reflects its monthly dosing maintaining protective serum concentrations throughout the RSV season, whereas nirsevimab’s single-dose schedule may result in waning protection over time. In conclusion, palivizumab demonstrates significantly greater effectiveness than nirsevimab in preventing RSV bronchiolitis in high-risk pediatric populations. These findings have important clinical and health policy implications, highlighting the need to weigh the convenience of single-dose administration against the superior protection provided by a multi-dose regimen. Head-to-head randomized trials and cost-effectiveness analyses are urgently needed to optimize prophylactic strategies.