Respiratory syncytial virus (RSV) remains a leading cause of lower respiratory tract infections in infants worldwide, often resulting in hospitalization during the first months of life. For years, preventive options were limited to passive immunoprophylaxis for high-risk infants, leaving most newborns vulnerable during peak RSV season. However, recent advances in maternal immunization have shifted the paradigm, offering a promising strategy to protect babies from birth by vaccinating their mothers during pregnancy.
According to the World Health Organization, RSV infects nearly all children by age two, with infants under six months facing the highest risk of severe disease. In 2019 alone, RSV was responsible for over 100,000 deaths in children under five globally, the majority occurring in low- and middle-income countries. The burden on healthcare systems is substantial, with RSV accounting for up to 20% of pediatric hospitalizations during winter months in temperate climates.
A pivotal clinical trial published in the New England Journal of Medicine in 2023 demonstrated that a single dose of the RSVpreF vaccine (marketed as Abrysvo) administered to pregnant individuals between 24 and 36 weeks’ gestation was 81.8% effective in preventing severe lower respiratory tract infection requiring medical intervention in infants through their first 90 days of life. Efficacy remained at 69.4% through six months of age. These findings were instrumental in regulatory decisions across multiple regions.
The U.S. Food and Drug Administration approved Abrysvo in August 2023 for use in pregnant individuals to prevent RSV in infants, becoming the first maternal vaccine approved for this indication. The European Medicines Agency followed with a positive opinion in October 2023, and the vaccine received full authorization in the European Union in January 2024. The World Health Organization’s Strategic Advisory Group of Experts on Immunization (SAGE) recommended in October 2023 that maternal RSV vaccination be considered in all countries, with priority given to settings where RSV poses a significant public health burden.
Real-world effectiveness data from the 2023–2024 RSV season in the United States, published by the Centers for Disease Control and Prevention in February 2024, showed that maternal RSV vaccination was associated with a 77% reduction in infant hospitalization due to RSV. Similar trends were observed in a multicenter European study coordinated by the European Centre for Disease Prevention and Control, which reported a 74% decrease in RSV-related hospital admissions among infants born to vaccinated mothers during the same period.
These results align closely with the 80% efficacy figure cited in early trial data and underscore the potential of maternal immunization to significantly reduce the strain on neonatal and pediatric intensive care units. Hospitals in countries with high vaccine uptake, such as Spain and Portugal, reported noticeable declines in RSV admissions starting in late 2023, according to national surveillance networks.
How Maternal RSV Vaccination Works
The RSVpreF vaccine is a stabilized prefusion F protein-based immunogen designed to elicit high levels of neutralizing antibodies against both RSV A and B subtypes. When administered during pregnancy, these antibodies are actively transported across the placenta, providing the fetus with passive immunity that peaks at birth and gradually wanes over the first six months of life — coinciding with the period of greatest vulnerability.
Unlike active infant vaccination, which faces challenges due to immature immune systems and interference from maternal antibodies, maternal immunization leverages the natural transfer of IgG antibodies to offer immediate protection. This approach has been successfully used for decades to prevent tetanus, diphtheria, and pertussis in newborns through vaccines like Tdap.
Safety data from over 3,600 pregnant participants in the pivotal trial showed no increase in preterm births, low birth weight, or neonatal adverse events compared to placebo. Post-authorization monitoring in the United States and Europe has not identified any safety signals of concern. The most commonly reported side effects were mild and included pain at the injection site, headache, and muscle pain — similar to those seen with other maternal vaccines.
The Advisory Committee on Immunization Practices (ACIP) in the United States recommends a single dose of RSVpreF vaccine during weeks 32 through 36 of pregnancy, administered seasonally from September through January in most of the continental U.S. To maximize protection during peak RSV circulation. In the European Union, national immunization technical advisory groups have issued similar guidance, with timing adjusted to local epidemiological patterns.
Global Access and Implementation Challenges
While high-income countries have begun rolling out maternal RSV vaccination programs, access remains limited in low-resource settings where the burden of disease is greatest. The vaccine’s current price point and cold chain requirements pose barriers to widespread adoption in regions with fragile health infrastructures.
Efforts are underway to address these disparities. The World Health Organization has included maternal RSV vaccination in its Immunization Agenda 2030 framework and is working with Gavi, the Vaccine Alliance, to explore financing mechanisms and tiered pricing for eligible countries. Preliminary discussions with the vaccine manufacturer, Pfizer, have indicated interest in developing access plans, though no formal commitments have been made public as of May 2024.
In the meantime, public health experts emphasize the importance of integrating RSV vaccination into existing prenatal care platforms. “Linking maternal RSV immunization with routine visits for Tdap, influenza, and COVID-19 vaccines can improve uptake and reduce missed opportunities,” said Dr. Ofer Levy, director of the Precision Vaccines Program at Boston Children’s Hospital, in a January 2024 interview with STAT News.
Community engagement and clear communication are likewise critical. Surveys conducted by the Kaiser Family Foundation in late 2023 found that while awareness of RSV is growing, many pregnant individuals remain uncertain about vaccine safety during pregnancy. Transparent dialogue with healthcare providers, supported by evidence-based counseling materials, is essential to building trust and acceptance.
What This Means for Families and Health Systems
For expectant parents, the availability of a maternal RSV vaccine offers a tangible way to reduce the risk of their newborn experiencing a serious respiratory illness in the first weeks of life. While no vaccine provides 100% protection, lowering the risk of hospitalization by approximately three-quarters represents a significant advance in infant preventive care.
From a systems perspective, reducing RSV hospitalizations frees up critical resources during peak respiratory illness seasons, when hospitals often face simultaneous surges of influenza, COVID-19, and RSV. Modeling studies suggest that widespread maternal RSV vaccination could prevent tens of thousands of infant hospitalizations annually in the United States alone, translating to substantial cost savings for healthcare systems.
Ongoing research is evaluating the long-term impact of maternal RSV vaccination, including potential effects on infant immune development and the possibility of extending protection beyond six months through booster strategies. Researchers are also investigating whether maternal vaccination could indirectly reduce RSV transmission in households and communities by decreasing the number of infected infants.
As RSV season approaches in the Northern Hemisphere, health authorities are urging pregnant individuals to consult with their obstetricians or midwives about vaccination timing and availability. Official recommendations and updates can be found through the Centers for Disease Control and Prevention, the European Centre for Disease Prevention and Control, and the World Health Organization.
The next major milestone in maternal RSV immunization will be the release of interim effectiveness data from the 2024–2025 RSV season by public health agencies in North America and Europe, expected in early 2025. These reports will help refine guidance on timing, dosing, and potential necessitate for revaccination in subsequent pregnancies.
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