The World Health Organization has achieved a significant milestone in global infant health by prequalifying Pfizer's maternal respiratory syncytial virus vaccine and issuing comprehensive recommendations for RSV prevention strategies worldwide.
First Maternal RSV Vaccine Receives WHO Prequalification
Pfizer's Abrysvo has become the first maternal RSV vaccine to receive WHO prequalification status, marking a crucial step toward expanding global access to RSV prevention. The vaccine works by preventing RSV-associated lower respiratory tract disease in infants during their first six months of life through the transfer of protective antibodies during gestation.
Previously, Abrysvo had only been available for maternal vaccination in high- and middle-income countries. The new prequalification status enables governments and international agencies such as Gavi and UNICEF to procure the vaccine for eligible low- and lower-middle-income countries, where the burden of RSV-related mortality is highest.
Global Disease Burden Drives Urgent Need
RSV represents a significant global health challenge, causing an estimated 100,000 deaths and over 3.6 million hospitalizations annually in children under five years of age. Half of these deaths occur in infants under six months, with 97% of fatalities concentrated in low- and middle-income countries where access to medical care remains limited.
Katherine O'Brien, WHO Director of Immunisation, Vaccines and Biologicals, emphasized the significance of this development: "RSV has long been an under-recognised public health problem, significantly impacting infants worldwide. Expanding access to maternal RSV vaccination will help keep infants out of hospitals, save lives and free up limited resources for other health priorities."
Comprehensive WHO Position Paper Released
WHO has published its first position paper on immunization products to protect infants from RSV in the Weekly Epidemiological Record. The document outlines recommendations for two distinct immunization approaches: a maternal vaccine (RSVpreF) and a long-acting monoclonal antibody (nirsevimab).
Both products received endorsement from the Strategic Advisory Group of Experts on Immunisation (SAGE) in September 2024, with the maternal vaccine subsequently receiving WHO prequalification in March 2025.
Clinical Implementation Guidelines
Maternal Vaccination Strategy
The maternal vaccine is recommended for pregnant women from 28 weeks of gestation onwards, ideally administered during routine antenatal visits. This timing allows for optimal transfer of protective antibodies to the developing fetus, providing protection during the critical first months of life when infants are most vulnerable to severe RSV disease.
Monoclonal Antibody Administration
Nirsevimab, administered as a single-dose monoclonal antibody, is recommended for infants at birth or before hospital discharge. In countries with defined RSV seasonality patterns, the antibody may be given to older infants before their first RSV season to provide targeted protection during peak transmission periods.
Strategic Implementation Considerations
WHO advises countries to select the immunization product that best aligns with their healthcare systems, taking into account factors including implementation feasibility, cost-effectiveness, and expected population coverage. The position paper serves as a comprehensive guide for national immunization strategies and provides critical information to inform funding decisions by national and international agencies.
The organization plans to launch an additional position paper in May based on SAGE's global recommendations for introducing passive immunization to prevent severe RSV disease in young infants. This document will provide further guidance for public health officials and immunization program managers on incorporating RSV immunization products into national programs.
