Maternal RSV Vaccine Shows 79% Protection Against Infant Hospitalization in Argentina
Real-world study of 505 infants shows maternal RSV vaccination during pregnancy dramatically reduces severe respiratory disease in babies.
Summary
Argentina's national maternal RSV vaccination program demonstrated remarkable real-world effectiveness in its first season. The BERNI study tracked 505 hospitalized infants and found that maternal vaccination with RSVpreF during pregnancy provided 78.6% protection against RSV-related respiratory disease requiring hospitalization in babies aged 0-3 months, with sustained 71.3% protection through 6 months. The vaccine also showed 76.9% effectiveness against severe disease. Notably, all three RSV-related infant deaths occurred in babies whose mothers weren't vaccinated, highlighting the life-saving potential of this maternal immunization strategy.
Detailed Summary
Argentina made history in March 2024 by becoming the first country to implement a national maternal RSV vaccination program, and the results are striking. This groundbreaking public health initiative demonstrates how maternal immunization can protect the most vulnerable infants during their first months of life.
The BERNI study followed 505 infants hospitalized with respiratory disease across 12 Argentine hospitals during the 2024 RSV season. Researchers used a test-negative case-control design, comparing babies who tested positive for RSV against those who tested negative, then analyzing whether their mothers had received the RSVpreF vaccine during pregnancy.
The results exceeded expectations. Maternal vaccination provided 78.6% protection against RSV hospitalization in infants aged 0-3 months, with effectiveness remaining strong at 71.3% through 6 months of age. For severe disease requiring hospitalization, protection reached 76.9%. Most significantly, all three RSV-related deaths occurred exclusively among infants whose mothers hadn't been vaccinated.
These findings validate maternal immunization as a powerful strategy for protecting newborns before they're old enough for direct vaccination. The timing window—vaccination between 32-36 weeks of pregnancy, at least 14 days before delivery—allows optimal antibody transfer to babies through the placenta.
While this study provides compelling real-world evidence, it's important to note the research was funded by Pfizer, the vaccine manufacturer, and several authors have industry ties. Additionally, this represents just one season of data from a single country's experience, though Argentina's implementation as a national program provides valuable insights for global maternal immunization strategies.
Key Findings
- Maternal RSV vaccination provided 78.6% protection against infant hospitalization (0-3 months)
- Protection remained strong at 71.3% effectiveness through 6 months of age
- Vaccine showed 76.9% effectiveness against severe RSV disease requiring hospitalization
- All three RSV-related infant deaths occurred in babies of unvaccinated mothers
- Argentina's national program represents first real-world implementation of maternal RSV vaccination
Methodology
Multicentre, retrospective, test-negative case-control study across 12 Argentine hospitals during 2024 RSV season. Compared 286 RSV-positive cases against 219 RSV-negative controls among hospitalized infants ≤6 months old, analyzing maternal vaccination status during pregnancy.
Study Limitations
Study funded by vaccine manufacturer Pfizer with several author conflicts of interest. Represents only one season of data from a single country. Long-term effectiveness and safety data still needed from broader populations and multiple seasons.
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