Systematic Review: Efficacy, Safety Profile, and Cost-Effectiveness of Nirsevimab Versus Palivizumab for RSV Prevention in Children Under 24 Months

<b>Background</b>: Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections (LRTI) in infants and young children, with significant morbidity, hospitalizations, and healthcare costs. Passive immunoprophylaxis has historically relied on palivizumab, while nirsevimab, a long-acting monoclonal antibody, has recently emerged as an alternative and has broader indications. <b>Methods:</b> We conducted a systematic review of randomized controlled trials, observational studies, real-world effectiveness analyses, and economic evaluations assessing the efficacy, safety, and cost-effectiveness of palivizumab and nirsevimab for RSV prevention in children under 24 months. <b>Results:</b> 41 studies were included in this review. Palivizumab demonstrated consistent efficacy in reducing RSV-related hospitalizations in high-risk infants, with relative risk reductions of approximately 45-55%. Nirsevimab showed higher relative efficacy, with reductions of 70-85% in RSV-associated lower respiratory tract infections and hospitalizations across randomized trials and real-world studies, including healthy term and late-preterm infants. Both monoclonal antibodies have favorable safety profiles, with adverse event rates comparable to the placebo. Economic analyses indicated that palivizumab is cost-effective primarily in narrowly defined high-risk populations, whereas nirsevimab may offer improved cost-effectiveness, particularly at lower acquisition prices and with seasonal administration strategies. <b>Conclusions:</b> Nirsevimab represents a promising advancement in RSV prevention, with broader protection, a simpler administration, and potential economic advantages compared to palivizumab.