Pediatrics · Medical Literature
RSV prophylactics for pediatric populations: A product review and meta-analysis of real-world effectiveness.
Abstract
Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection and hospitalization in infants and young children worldwide. Clinical management in infants remains primarily supportive, and natural infection provides incomplete and transient immunity. For decades, prophylaxis was limited to monthly palivizumab for selected high-risk infants. Recent advances in prefusion F structural biology, antibody engineering, and maternal immunization have transformed RSV prevention. This review summarizes the biologic and clinical rationale for preventing RSV disease in pediatric populations, with emphasis on currently licensed long-acting monoclonal antibodies and maternal RSVpreF vaccination. We integrate a meta-analysis of real-world effectiveness data and discuss implementation of these novel immunoprophylactic strategies in clinical practice. Across 43 observational studies, pooled effectiveness against RSV-associated hospitalization was 80.9% for nirsevimab and 79.1% for maternal RSVpreF vaccination, demonstrating substantial real-world protection during early infancy. Success now depends on optimizing implementation and achieving equitable access.
Clinical relevance
What is the real-world effectiveness of currently licensed RSV prophylactic strategies — nirsevimab and maternal RSVpreF vaccination — in preventing RSV-associated hospitalization in infants and young children? __SNAPSHOT__ {"studyDesign":"Structured narrative review with integrated systematic review and product-specific meta-analyses of observational (real-world) studies","setting":"International; meta-analysis includes studies published from January 2015 through May 2026; individual constituent studies drawn from multiple high-income countries (including the United States, France, Spain, Italy, Luxembourg, and Australia)","sampleSize":"43 observational studies included across the meta-analysis (38 nirsevimab studies + 5 RSVpreF maternal vaccine studies); individual study-level sample sizes not reported in the abstract","population":"Infants and young children during their first RSV season; includes both term and preterm infants. Specific inclusion criteria for constituent studies not detailed in the abstract.","intervention":"Nirsevimab (long-acting monoclonal antibody targeting RSV prefusion F site Ø; EU approval 2022, US approval 2023) and maternal RSVpreF vaccination (bivalent prefusion-stabilized F subunit vaccine; US approval 2023), each analyzed in separate product-specific meta-analyses","comparator":"Unimmunized or unvaccinated infants (observational controls within constituent real-world effectiveness studies)","primaryOutcome":"RSV-associated hospitalization (prevention thereof); pooled vaccine/prophylactic effectiveness reported separately for each product","followUp":"Varies by constituent study; overall search period January 2015–May 2026; individual study follow-up durations not reported in the abstract","fundingSource":"Not reported in the abstract or the publicly available article excerpt"}
Key findings
Across 43 observational studies, the pooled real-world effectiveness (random-effects model) against RSV-associated hospitalization was 80.9% for nirsevimab and 79.1% (95% CI: 73.6%–83.5%) for maternal RSVpreF vaccination. For the RSVpreF meta-analysis (5 studies: Gentile 2025, McLachlan 2026, Moline 2026, Pérez Marc 2025, Williams 2025), individual study estimates ranged from 70.0% (95% CI: 36.4%–85.9%) to 82.2% (95% CI: 75.4%–87.1%), with low heterogeneity (I² = 1.3%, τ² = 0.001, Cochran Q p = 0.611). A 95% CI for the pooled nirsevimab estimate is not reported in the abstract; only the point estimate of 80.9% is stated. Risk-of-bias assessments showed most included studies had low or moderate risk of bias, with the most frequent concerns relating to confounding and participant selection. Funnel plot assessment and formal asymmetry testing did not suggest publication bias among nirsevimab studies. Certainty of evidence using GRADE was rated as moderate for both nirsevimab and RSVpreF, though the basis for this rating is not fully detailed in the available text. Absolute risk reduction, NNT, and adverse event data are not reported in the abstract. Clesrovimab was not included in the meta-analysis, as no post-licensure effectiveness studies were available at the time of the search.
Practice implications
This review and meta-analysis establishes that both nirsevimab and maternal RSVpreF vaccination achieve substantial real-world protection against RSV-associated hospitalization in infants (~79–81% pooled effectiveness), a finding that is consistent across multiple high-income country settings and corroborated by independent meta-analyses. However, several important interpretive constraints apply: (1) Only the abstract was reviewed; full methodology, subgroup analyses, and sensitivity analyses are not available to this summary. (2) The 43 constituent studies are entirely observational, meaning unmeasured confounding (e.g., health-seeking behavior, gestational age distribution, socioeconomic status) could inflate effectiveness estimates; the authors themselves note confounding and participant selection as the most frequent risk-of-bias concerns. (3) GRADE certainty was moderate for both products, appropriately reflecting these observational-design limitations. (4) The RSVpreF meta-analysis included only 5 studies, limiting precision and generalizability for that intervention. (5) Clesrovimab, approved in the US in June 2025, was not evaluable. (6) Data are drawn almost exclusively from high-income countries; applicability to low- and middle-income settings — where the majority of RSV mortality occurs — is not established. (7) Effectiveness against severe outcomes (PICU, mechanical ventilation, death) and duration of protection are not addressed in the abstract. (8) The review does not directly compare nirsevimab against maternal RSVpreF vaccination; the point estimates are numerically similar and no head-to-head comparative inference is appropriate from this aggregate analysis. Overall, findings strongly support continued use of both strategies in eligible infants and are consistent with regulatory approvals and prior systematic reviews, but should be interpreted as confirmatory of existing evidence rather than paradigm-shifting. __LIMITATIONS__ Only the abstract was available for review; full methodology, PRISMA flow, and subgroup analyses were not independently verifiable.,All constituent studies are observational (cohort or case-control); residual confounding — particularly by gestational age, baseline risk, health-seeking behavior, and immunization timing — cannot be excluded and may inflate effectiveness estimates.,Risk-of-bias assessments identified confounding and participant selection as the most frequent concerns across included studies.,The RSVpreF maternal vaccine meta-analysis is based on only 5 studies, limiting stability of the pooled estimate and statistical power to detect heterogeneity.,Studies are predominantly from high-income European and North American countries; findings may not generalize to low- and middle-income countries or to populations with different RSV seasonality.,Absolute risk reductions and NNT are not reported, limiting direct assessment of clinical magnitude.,No 95% CI for the nirsevimab pooled effectiveness estimate (80.9%) is reported in the abstract.,Duration of protection, effectiveness against severe outcomes (PICU, mechanical ventilation), and effectiveness beyond the first RSV season are not addressed.,Clesrovimab — a newly licensed alternative monoclonal antibody — is excluded due to absence of post-licensure effectiveness data, creating a gap for clinicians considering this agent.,Funding source for this review is not reported; potential conflicts of interest of individual authors cannot be assessed from the abstract alone.,Heterogeneity in individual study designs, RSV ascertainment methods, immunization timing, and coverage rates may limit the precision of pooled estimates, despite low I² in the RSVpreF analysis. __BOTTOM_LINE_CATEGORY__ confirmatory __BOTTOM_LINE__ This meta-analysis of 43 real-world observational studies demonstrates high pooled effectiveness of nirsevimab (~80.9%) and maternal RSVpreF vaccination (~79.1%; 95% CI: 73.6%–83.5%) against RSV-associated hospitalization in infants, with low heterogeneity for the RSVpreF analysis and moderate GRADE certainty for both products. These findings corroborate prior systematic reviews and support current recommendations for universal or broad infant RSV immunoprophylaxis in high-income settings. Successful implementation now depends on achieving equitable access and high coverage, particularly in populations and countries where uptake remains suboptimal.