Sanofi Highlights New Evidence Showing Beyfortus Protection for Infants Extends Across Two RSV Seasons

(IN BRIEF) Sanofi reported new real-world evidence showing that immunization with Beyfortus can significantly reduce RSV-related hospitalizations not only during an infant’s first RSV season but also into the second year of life. The NIRSE-GAL study in Galicia, Spain, demonstrated high program coverage and an 85.9 percent decline in severe RSV hospitalizations during the first season, followed by a further 55.3 percent reduction in the second season among previously immunized children. Additional findings included fewer outpatient respiratory illnesses and rehospitalizations, suggesting that preventing early infection may support healthier lung development and longer-term protection. The results, published in The Lancet Infectious Diseases and presented at RSVVW ’26, provide important population-level insights for shaping future infant RSV prevention strategies.

(PRESS RELEASE) PARIS, 16-Feb-2026 — /EuropaWire/ — Sanofi announced new findings demonstrating that early immunization of infants with Beyfortus (nirsevimab) against respiratory syncytial virus (RSV) may provide protective benefits that extend beyond the first RSV season. The results, published in The Lancet Infectious Diseases and presented at the RSVVW ’26 conference in Rome, represent the first prospective real-world evidence showing fewer RSV-related hospitalizations in a second season among infants who received immunization during their first year of life.

The NIRSE-GAL population study, carried out in Galicia, Spain, evaluated the outcomes of a universal RSV immunization program over two consecutive seasons. Researchers compared observed hospitalization rates among immunized infants with expected figures based on historical seasonal data, revealing sustained clinical impact beyond the initial protection window.

Program uptake reached 94.4 percent of eligible infants, with 11,796 of 12,492 children receiving immunization. During the first RSV season, the study recorded an 85.9 percent reduction in hospitalizations associated with RSV-related lower respiratory tract infections. In the second season, infants immunized during infancy experienced 55.3 percent fewer RSV hospitalizations than expected, indicating that preventing severe infection during early lung development may contribute to improved respiratory health later in childhood.

The analysis also identified reductions in primary care visits during the first season, including fewer consultations for bronchitis, bronchiolitis, lower respiratory tract infections, wheezing, and asthma-related symptoms. Among infants previously hospitalized due to RSV, rehospitalizations declined markedly in the following season, supporting the hypothesis that early protection may deliver lasting benefits by limiting initial lung damage.

About RSV
RSV is a highly contagious virus that can lead to serious respiratory illness for infants. Two out of three infants are infected with RSV during their first year of life and almost all children are infected by their second birthday. RSV is the most common cause of lower respiratory tract disease, including bronchiolitis and pneumonia, in infants. It is also a leading cause of hospitalization in infants worldwide, with most hospitalizations for RSV occurring in healthy infants born at term. Globally, in 2019, there were approximately 33 million cases of acute lower respiratory infections leading to more than three million hospitalizations in children younger than five years. RSV-related direct medical costs, globally — including hospital, outpatient and follow-up care — were estimated at c.€5 billion in 2017.

About Beyfortus
Beyfortus is the first immunization designed for all infants for protection against RSV disease through their first RSV season, including for those born before or during the RSV season, healthy at term or preterm, or with specific health conditions. Beyfortus is also designed to protect children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

As a long-acting antibody provided directly to newborns and infants as a single dose, Beyfortus offers rapid and direct protection to help prevent lower respiratory tract disease caused by RSV without requiring activation of the immune system. Beyfortus administration can be timed to coincide with the RSV season.

Beyfortus has been approved for use in the US, the EU, China, Japan, and many other countries around the world. Special designations to facilitate expedited development of Beyfortus were achieved in several countries, including breakthrough therapy designation and fast track designation in the US; PRIority MEdicines (PRIME) and accelerated assessment in the EU; “a medicine for prioritized development” in Japan, and breakthrough therapy designation and priority review designation in China.

About REACH
The REACH study was performed on the LOGEX RTI Observatory, ran by healthcare analytics company LOGEX, and used administrative and microbiology data from multiple hospital sites across Spain and the UK. Data collection is ongoing through May 2025, with current results reflecting three consecutive RSV seasons from June 2022 through the end of March 2025. Hospitals report RSV hospitalizations from the current season as well as historical seasons for each country separately. No RSV prevention program was in place for the 2022-23 RSV season.

About HARMONIE
The Hospitalized RSV Monoclonal Antibody Prevention (HARMONIE) study is a large European Phase 3b clinical trial conducted in multi-country, close to real-world conditions to reinforce the efficacy and safety of Beyfortus for the prevention of RSV-related hospitalizations in infants up to 12 months of age who are not eligible to receive palivizumab.

The trial opened at nearly 250 sites and enrolled more than 8,000 infants born with a gestational age of 29 weeks or greater during the 2022-2023 RSV season. Primary results from the study published in The New England Journal of Medicine (NEJM) confirmed efficacy of 83.2% (95% CI 67.8 to 92.0; P<0.001) for Beyfortus against RSV-related hospitalizations and efficacy of 75.7% (95% CI: 32.8 to 92.9; P=0.004) against very severe RSV lower respiratory tract disease compared to no RSV intervention (standard of care) through the RSV season.

About Sanofi
Sanofi is an R&D driven, AI-powered biopharma company committed to improving people’s lives and creating compelling growth. We apply our deep understanding of the immune system to invent medicines and vaccines that treat and protect millions of people around the world, with an innovative pipeline that could benefit millions more. Our team is guided by one purpose: we chase the miracles of science to improve people’s lives; this inspires us to drive progress and deliver positive impact for our people and the communities we serve, by addressing the most urgent healthcare, environmental, and societal challenges of our time.

Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY

Sanofi forward-looking statements
This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements are statements that are not historical facts. These statements include projections and estimates regarding the marketing and other potential of the product, or regarding potential future revenues from the product. Forward-looking statements are generally identified by the words “expects”, “anticipates”, “believes”, “intends”, “estimates”, “plans”, and similar expressions. Although Sanofi’s management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, unexpected regulatory actions or delays, or government regulation generally, that could affect the availability or commercial potential of the product, the fact that product may not be commercially successful, the uncertainties inherent in research and development, including future clinical data and analysis of existing clinical data relating to the product, including post marketing, unexpected safety, quality or manufacturing issues, competition in general, risks associated with intellectual property and any related future litigation and the ultimate outcome of such litigation, and volatile economic and market conditions, and the impact that global crises may have on us, our customers, suppliers, vendors, and other business partners, and the financial condition of any one of them, as well as on our employees and on the global economy as a whole. The risks and uncertainties also include the uncertainties discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements” in Sanofi’s annual report on Form 20-F for the year ended December 31, 2024. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-looking information or statements.

Sanofi Highlights New Evidence Showing Beyfortus Protection for Infants Extends Across Two RSV Seasons

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