One step closer to protection: Setting the stage for maternal RSV vaccine introduction
2025 has been a significant year in the journey towards respiratory syncytial virus (RSV) prevention. In March, the World Health Organization (WHO) prequalified a maternal RSV vaccine (Abrysvo®, Pfizer, Inc.), recommending its global use. The Pan American Health Organization (PAHO) has also endorsed the vaccine. In July, Gavi, the Vaccine Alliance, pledged to open a funding window for an RSV maternal immunization program, a milestone in introducing it in low- and middle-income countries (LMICs).
With the WHO's prequalification of the single-dose vial of the maternal vaccine, countries are now encouraged to explore strategies for introducing vaccines and other RSV prevention tools. A crucial next step is to expedite the pathway to WHO prequalification for a multi-dose vial presentation, better suited for low- and middle-income markets, potentially as early as 2026. While long-acting monoclonal antibodies are also WHO-recommended for protecting infants from RSV, price and supply remain barriers in many LMICs, necessitating market shaping to overcome these challenges.
WHO's recommendations and guidance provide a solid foundation for countries embarking on this journey. Despite the considerable time before the maternal vaccine is introduced in LMICs, preparations are underway, ensuring countless children will benefit in the future.
Vaccinating mothers, protecting newborns
RSV is the leading cause of severe respiratory infections and hospitalizations in infants and young children, with nearly all children contracting it before their second birthday. Striking disparities exist in RSV mortality between low- and high-income settings: 98% of pediatric RSV deaths occur in low- and middle-income economies, and many children never reach the hospital.
Clint Pecenka, director of PATH's RSV vaccine project, emphasizes the impact of RSV in low-resource settings, where some children never receive care. Maternal vaccination offers a vital solution, safeguarding babies early and alleviating pressure on families and health systems.
Preventing severe RSV disease is paramount. The maternal RSV vaccine, administered during pregnancy, enhances a pregnant woman's immunity and facilitates natural antibody transfer to the baby in their initial months. WHO recommends vaccination in the third trimester of pregnancy, as per local guidelines.
The potential impact of RSV vaccines on children
Pfizer's maternal vaccine has demonstrated remarkable efficacy in clinical trials. A Phase 3 study revealed sustained protection through six months post-birth, with 82% efficacy in the first 90 days and 70% after 180 days. These findings indicate the vaccine's ability to safeguard children during their first six months, when RSV poses the greatest threat to their health.
Real-world data from countries introducing the maternal RSV vaccine, such as Argentina, confirm high vaccine effectiveness, particularly against severe disease. RSV places a significant strain on health systems and households, leading to millions of hospitalizations and burdening parents and caregivers. Maternal vaccines not only prevent hospitalizations but also reduce healthcare costs and free up resources for other health priorities.
Ranju Baral, a senior health economist at PATH, highlights the cost-effectiveness of delivering new maternal vaccines like RSV in Kenya, Ghana, and Mozambique. Modeling studies suggest these vaccines can be cost-effective in many LMICs, pending vaccine pricing for LMIC markets. Optimism surrounds the potential of maternal RSV vaccines as a smart investment in maternal and child health in regions where they are most needed.
Expanding access to maternal vaccines
WHO's recent RSV vaccine recommendations build upon a strong history of maternal immunization. Maternal vaccines for diseases like tetanus, influenza, and pertussis have proven effective for years, with new ones in development for pathogens such as Group B Streptococcus. Maternal vaccines offer unique advantages, providing protection for two individuals and benefiting infants too young for certain vaccines.
As more maternal vaccines emerge, PATH conducts research in Africa to assess adoption readiness, exploring delivery requirements in Ghana, Senegal, Tanzania, and Zambia. PATH's research in these countries, along with Mozambique, Vietnam, and five PAHO region countries, enhances understanding of how current antenatal care visit timing aligns with recommended RSV maternal vaccination windows, informing implementation decisions.
Controversial Considerations and Next Steps
The introduction of maternal RSV vaccines raises crucial questions regarding antenatal care and immunization program intersections. Sadaf Khan, a program advisor for maternal, newborn, and child health at PATH, emphasizes the need to identify potential programmatic challenges, workforce readiness, and other gaps to ensure countries are prepared for vaccine rollout.
With the single-dose vial presentation of maternal RSV vaccines prequalified, prioritizing planning for their rollout is essential, especially as RSV is a novel disease target for many countries. As countries plan for RSV prevention, they must consider the local impact of the disease, the cost and benefits of available products, and their integration into health systems. Expanding RSV surveillance efforts will enable countries to advocate for vaccine introduction and pinpoint areas of maximum impact.
Key steps include preparing delivery platforms through antenatal care and immunization programs, raising awareness among healthcare providers and caregivers, and ensuring systems are ready to monitor safety and effectiveness. Long-term success relies on workforce readiness and securing funding.
WHO, PATH, and other contributors have developed a comprehensive suite of communication materials covering RSV disease, new prevention tools, and delivery considerations. These resources support informed decision-making and implementation planning around RSV and relevant interventions.
Maternal RSV vaccines hold immense potential to protect infants from a deadly threat that has long been overlooked. By setting the stage for introduction, we can ensure countries are well-prepared to implement this life-saving intervention in the years to come.
