A landmark real-world study from Spain confirms nirsevimab cuts RSV hospitalizations by 86% in the first season while delivering lasting protection into the second year of life.
February 2026- Every winter,Respiratory Syncytial Virus (RSV) sends thousands of babies to hospital. But new evidence from Spain suggests a single immunization during infancy could change that picture not just for one season, but two.
A study published in The Lancet Infectious Diseases followed nearly 12,000 infants in Galicia, Spain, who received Beyfortus (nirsevimab) as part of a universal RSV immunization program. The results were striking. During the first RSV season, hospitalizations linked to lower respiratory tract infections dropped by 85.9%. That alone would be considered a success. What surprised researchers was what happened next.
Infants who had been immunized in their first season were 55.3% less likely to be hospitalized for RSV when the following season arrived. Scientists believe that protecting young lungs during those earliest months , a period when respiratory development is at its most vulnerable which may reduce the risk of severe illness later on.
The program’s reach was broad, with 94.4% of eligible infants receiving the immunization, a coverage figure that public health officials rarely achieve in practice.
“This universal RSV immunization program with Beyfortus showed decreased RSV-related hospitalizations and outpatient illness burden during the first season, with persistent impact seen on RSV hospitalizations through the second season,” said Federico Martinón-Torres, Head of Pediatrics at Santiago University Hospital in Spain, and principal investigator of the NIRSE-GAL study.
The NIRSE-GAL study is the first of its kind to track outcomes across two consecutive RSV seasons at a population level, making its findings particularly valuable for governments and health authorities weighing the long-term case for universal infant immunization.
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“This study builds upon our wealth of evidence supporting the public health value of a Beyfortus immunization program, It’s exciting to see the significant impact of this infant immunization program during the first RSV season and truly remarkable to consider a benefit across two seasons ” said Thomas Triomphe, Executive Vice President, Vaccines, Sanofi”.
The findings were presented at the RSVVW ’26 conference in Rome, Italy, and are published in full in The Lancet Infectious Diseases.
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