Maternal RSV Shot Cuts Infant Hospital Risk by 80%, UK Study Confirms

MUNICH, Germany – April 18, 2026 – A groundbreaking study presented today has delivered the most compelling real-world evidence to date on the power of maternal vaccination against Respiratory Syncytial Virus (RSV), showing it can reduce the risk of an infant being hospitalized with the virus by more than 80%.

The findings, unveiled at the prestigious ESCMID Global 2026 congress, come from a massive analysis of nearly 300,000 infants by the UK Health Security Agency (UKHSA). They provide a powerful validation for England's national maternal RSV vaccination program, which was launched on September 1, 2024, and offer a potential blueprint for global health policy.

RSV is a notoriously common and dangerous virus for the very young, representing the leading cause of infant hospitalization worldwide. The virus can lead to severe respiratory illnesses like bronchiolitis and pneumonia, and early-life infections have been linked to long-term health issues, including asthma. Globally, RSV is responsible for an estimated 3.6 million hospitalizations and tragically, around 100,000 deaths in children under five each year, with the vast majority occurring in low- and middle-income countries.

A Shield for the Most Vulnerable

The UKHSA study offers a beacon of hope in the fight against this pervasive threat. Researchers conducted a retrospective cohort study using linked national health datasets, covering approximately 90% of all births in England between September 2024 and March 2025.

Among the 289,399 infants included, the data painted a stark picture. Infants born to unvaccinated mothers, who made up 55% of the cohort, accounted for a staggering 87.2% of the 4,594 RSV-related hospitalizations.

In sharp contrast, infants whose mothers received Pfizer's Bivalent Prefusion F vaccine, marketed as Abrysvo, at least 14 days before giving birth saw their risk of hospitalization plummet. The study calculated an overall vaccine effectiveness of 81.3% compared to the unvaccinated group.

"As the largest study to date examining the impact of this vaccine on infant hospitalisation, these findings provide robust evidence that vaccination offers substantial protection against severe illness in young infants," said Matt Wilson, the study's lead author and an epidemiologist with UKHSA, in a statement.

The research also highlighted the importance of timing. "We found a clear relationship between timing and protection, with effectiveness increasing as the interval between vaccination and birth lengthens, reaching close to 85% when vaccination occurs at least four weeks before delivery," Wilson explained. This demonstrates that vaccination provides a powerful shield of passive immunity, as protective antibodies are transferred from mother to fetus during the final weeks of pregnancy.

Even for preterm infants, who are at a significantly higher risk of severe RSV, the vaccine proved highly effective. The study found a vaccine effectiveness of 69.4% in this vulnerable group, provided there was a window of at least two weeks between vaccination and birth. "These findings are particularly important for preterm infants," Wilson added. "With sufficient time between vaccination and birth, we saw good levels of protection in these babies."

From Clinical Trials to Real-World Triumph

The success of the UK's program builds on a foundation of rigorous clinical trials and a new wave of preventative tools against RSV. Pfizer's Abrysvo vaccine received landmark approvals from both the U.S. Food and Drug Administration (FDA) and the European Commission in August 2023 for use in pregnant individuals to protect their infants.

Those approvals were based on clinical trial data that showed the vaccine reduced the risk of severe RSV-related lower respiratory tract disease by 81.8% within 90 days of birth. However, the trials also noted a slight, though not statistically significant, numerical imbalance in preterm births. This prompted regulatory bodies like the FDA to recommend a specific vaccination window of 32 to 36 weeks gestation to mitigate any potential risk while maximizing the transfer of protective antibodies.

The UKHSA's real-world data now provides crucial reassurance and reinforces the vaccine's safety and effectiveness outside the controlled environment of a clinical trial. This type of large-scale evidence is vital for building confidence among healthcare providers and the public, confirming that the benefits of preventing severe, and sometimes fatal, infant illness far outweigh theoretical risks.

A Blueprint for Global Health?

The success in England is being watched closely around the world, as health systems grapple with the immense burden of RSV. The UK's strategy is part of a broader global shift towards proactive RSV prevention. In the United States, the Centers for Disease Control and Prevention (CDC) also recommends seasonal maternal RSV vaccination.

This new vaccination strategy joins a growing arsenal of prevention tools. For decades, the main option for high-risk infants was palivizumab, a costly monoclonal antibody requiring monthly injections. More recently, new long-acting monoclonal antibodies like nirsevimab have been approved, offering protection for an entire RSV season with a single shot for all infants.

Public health bodies, including the World Health Organization (WHO), now recommend that countries implement either a maternal vaccination program or provide infant monoclonal antibodies, depending on cost-effectiveness and infrastructure. The WHO's endorsement and prequalification of the maternal vaccine in March 2025 has paved the way for its procurement and use in lower-income nations where the RSV burden is heaviest.

While the path to global adoption has challenges, including cost, logistical hurdles, and the need for public education, the UKHSA study provides a powerful piece of the puzzle. It demonstrates that a well-implemented national maternal vaccination program is not just a theoretical goal but a practical, life-saving reality that can significantly reduce the strain on pediatric hospitals and protect the world's youngest and most vulnerable citizens.