The World Health Organization (WHO) has issued its first official position paper recommending immunization products to protect infants from respiratory syncytial virus (RSV)—the leading cause of acute lower respiratory infections among young children worldwide.
RSV is responsible for around 100,000 deaths and over 3.6 million hospitalizations annually in children under five. Infants younger than six months are the most vulnerable, and 97% of RSV-related deaths occur in low- and middle-income countries with limited access to medical support like oxygen and hydration.
Published in the Weekly Epidemiological Record (WER), WHO’s position paper recommends two immunization options: a maternal vaccine that can be given to pregnant women in their third trimester to protect their infant and a long-acting monoclonal antibody that can be administered to infants from birth, just before or during the RSV season.
RSV: Mild Symptoms, Serious Risks
RSV often causes symptoms like runny nose, cough, and fever. However, in infants and vulnerable groups, it can lead to serious complications such as bronchiolitis and pneumonia, often requiring hospitalization.
“RSV is an incredibly infectious virus that’s especially dangerous to premature infants,” said Dr. Kate O’Brien, WHO Director of Immunization, Vaccines, and Biologicals at WHO. “These recommended immunization products can save many infant lives and reduce hospitalizations globally.”
Two Immunization Options
To address the global burden of RSV, WHO recommends countries implement either the maternal vaccine RSVpreF or the monoclonal antibody nirsevimab based on feasibility, health system capacity, cost-effectiveness, and expected coverage.
The maternal vaccine, which received WHO prequalification in March 2025, is given from the 28th week of pregnancy onward during routine antenatal visits. This approach ensures effective transfer of protective antibodies to the infant before birth, offering immunity from day one.
The monoclonal antibody, nirsevimab, is a single injection given directly to newborns—either immediately after birth or during the first health visit. It provides rapid protection within a week and lasts at least five months, covering the RSV season. It can also be administered to older infants just before their first RSV season, if not given at birth.
The highest impact in preventing severe RSV disease is expected when nirsevimab is administered to infants under six months of age, although benefits extend to those up to 12 months.
These recommendations were endorsed by WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) in September 2024. By supporting early protection through maternal vaccination or monoclonal antibodies, WHO aims to help countries, especially those with limited healthcare access, dramatically reduce the global burden of RSV.
WHO’s position paper serves as guidance for national policymakers, immunization programme managers, and international funding bodies to integrate RSV immunization products into existing public health strategies.
