On 12 March 2025, the World Health Organization (WHO) prequalified the first maternal respiratory syncytial virus (RSV) vaccine to protect infants against one of the most common causes of acute lower respiratory infections in children globally.
Each year, RSV causes more than 3.6 million hospitalizations and about 100 000 deaths in children under 5 years of age. About half of these deaths occur in infants younger than 6 months of age. The majority of paediatric RSV deaths occur in low- and middle-income countries where there is limited access to supportive medical care.
Currently, there are no specific treatments for RSV infection, making supportive measures the main line of therapy. Preventive measures, such as vaccines, are key to reducing cases of pneumonia and bronchiolitis, decreasing hospitalizations and oxygen use, and saving infant lives globally. After decades of research, there are currently two licensed immunization products for prevention of RSV disease in young infants: the maternal vaccine given to pregnant women in the third trimester to protect their babies and a long-acting monoclonal antibody administered to infants from birth just before or during the RSV season.
"RSV has long been an under-recognized public health problem, significantly impacting infants worldwide," says Dr Katherine O'Brien, WHO Director, Immunization, Vaccines and Biologicals. "Expanding access to maternal RSV vaccination will help keep infants out of hospitals, save lives and free up limited resources for other health priorities."
In September 2024, the Strategic Advisory Group of Experts on Immunization (SAGE) made global recommendations to introduce passive immunization (maternal vaccination and infant monoclonal antibodies) for the prevention of severe RSV disease in young infants. The subsequent prequalification of the maternal RSV vaccine in March 2025 reflects the Organization's commitment to improving health equity by expediting access to life-saving health products in parallel to developing recommendations.
The prequalified maternal vaccine, ABRYSVO®, aims to prevent RSV-associated disease in infants during the first 6 months through the transfer of antibodies during gestation. ABRYSVO® is manufactured by Pfizer with the European Medicines Agency (EMA) as the Regulatory Authority of reference. To date, the maternal RSV vaccine has only been used in high- and middle-income countries. With prequalification and new WHO recommendations, the aim is to expand RSV vaccination to low- and lower-middle-income countries where the risk of severe disease and death is highest.
WHO will launch a position paper on RSV vaccines in May 2025 based on the SAGE recommendations. The aim of the position paper is to inform national public health officials and immunization programme managers on use of RSV immunization products in their national programmes, as well as national and international funding agencies.
Prequalification is a pre-requisite for financial support from Gavi, the Vaccine Alliance, and for vaccine purchases by UN agencies such as UNICEF. The Gavi Board will make further decisions about the inclusion the maternal RSV vaccine within the Organization's vaccine portfolio during 2025.
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