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, marking a milestone in the introduction of the vaccine 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 process of achieving WHO prequalification for a multi-dose vial presentation, better suited for low- and middle-income markets, which could be achieved as early as 2026. (Long-acting monoclonal antibodies are also WHO-recommended for protecting infants from RSV, but price and supply remain barriers to access for many LMICs, necessitating market shaping to overcome these challenges.)
WHO's recommendations and guidance serve as a foundation for countries embarking on this journey. While the introduction of the maternal vaccine in LMICs may still be some time away, the stage is set for preparations that will ultimately benefit countless children.
Vaccinating mothers, protecting newborns
RSV is the primary cause of severe respiratory infections and hospitalizations in infants and young children. Its widespread nature means nearly all children contract it before their second birthday. Striking disparities exist in RSV mortality rates 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.
"RSV is a significant cause of infant illness and death, especially in low-resource settings where some children never even receive care," said Clint Pecenka, director of PATH's RSV vaccine project. "Maternal vaccination offers a vital opportunity to reduce this burden, protecting babies early and alleviating the pressure on families and health systems."
In this context, 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 of life. The WHO globally recommends vaccination in the third trimester of pregnancy, as outlined in local guidelines.
What RSV vaccines could mean for children
Pfizer's maternal vaccine has demonstrated impressive efficacy in clinical trials. A Phase 3 study revealed that protection from the vaccine persists for up to 6 months after birth, with 82% efficacy in the first 90 days and 70% after 180 days. These findings indicate that the vaccine can effectively safeguard children during their first 6 months of life, when RSV poses the greatest threat to their health.
Real-world data from countries that have introduced the maternal RSV vaccine, such as Argentina, further validate its high effectiveness, particularly against severe disease.
Moreover, RSV places a substantial strain on health systems and households, leading to millions of hospitalizations and burdening parents and caregivers. Introducing maternal vaccines could not only prevent hospitalizations but also reduce healthcare costs and free up resources for other health priorities.
"Our cost-of-delivery analyses in Kenya, Ghana, and Mozambique indicate that the estimated costs of delivering new maternal vaccines like RSV are comparable to those of routine childhood vaccines," said Ranju Baral, a senior health economist at PATH. "Modeling studies also suggest that these vaccines can be cost-effective in many LMICs, a prediction that will be confirmed once vaccine pricing for LMIC markets becomes available. In essence, there's reason to be optimistic that maternal RSV vaccines could be a wise investment in maternal and child health where they are most needed."
Expanding access to maternal vaccines
The WHO's recent RSV vaccine recommendations build upon a strong track record of maternal immunization. Maternal vaccines for diseases like tetanus, influenza, and pertussis have been making a difference for years, and new ones are in development for pathogens such as Group B Streptococcus. Maternal vaccines offer distinct advantages, providing protection for two individuals simultaneously and aiding infants too young to receive certain vaccines.
As more maternal vaccines become available, PATH is conducting research in Africa to gain a comprehensive understanding of adoption readiness. This research explores delivery requirements in Ghana, Senegal, Tanzania, and Zambia. PATH's studies in these countries, along with Mozambique, Vietnam, and five countries in the PAHO region, are also enhancing our understanding of how current antenatal care visit timing aligns with recommended RSV maternal vaccination windows to inform implementation decisions.
Controversial Considerations and Next Steps
The introduction of maternal RSV vaccines raises important considerations and potential controversies. One key aspect is the intersection of antenatal care and immunization programs. Understanding how these programs interact is crucial for identifying potential challenges, workforce readiness, and other gaps that countries may face when implementing these vaccines. Sadaf Khan, a program advisor for maternal, newborn, and child health at PATH, emphasizes the importance of this understanding.
As countries begin planning for RSV prevention, they must consider the local impact of the disease, the cost-effectiveness of available products, and how well these products integrate into their health systems. Expanding RSV surveillance efforts will enable countries to make a case for vaccine introduction and better understand the areas where they can have the most significant impact.
Other critical 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 also relies on workforce readiness and securing funding.
To support informed decision-making and implementation planning, WHO, PATH, and other contributors have developed a suite of communications materials covering RSV disease, new prevention tools, and delivery considerations. These resources can provide valuable insights into 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 that countries are well-prepared to implement this life-saving intervention in the years to come.
