A recent study published in JAMA Network reveals that nearly 80% of infants born during the late 2023 and early 2024 respiratory syncytial virus (RSV) season received protection against the virus.
Infants born before December mainly received nirsevimab, while those born after October 25 were given maternal RSVpreF, a vaccine for pregnant women. RSVpreF, approved in August 2023, is administered to women between 32 and 36 weeks of pregnancy and helps pass immunity to their babies. Nirsevimab, approved in July 2023, is a long-acting antibody that provides targeted protection to infants under eight months old.
As of January 2025, RSV activity has surged among young children, contributing to a spike in respiratory illnesses. Emergency department visits for RSV and flu have increased, while COVID-19 cases remain low.
Initially, access to both nirsevimab and RSVpreF faced challenges, but they have become more widely available, particularly through Kaiser Permanente Northern California (KPNC), helping to address health disparities.
Researchers analyzed the electronic medical records of 17,251 infants born to mothers aged 15 to 49 between October 2023 and March 2024. The study looked at factors such as the mother’s age, race, insurance, and prenatal care.
The results showed that 77.5% of infants received protection from either RSVpreF or nirsevimab. Of those, 33.9% were exposed only to RSVpreF, while 40.9% received only nirsevimab, and about 2% were exposed to both. The study also found that 31.1% of infants exposed to both vaccines were born preterm, and 24.1% required neonatal intensive care.
Timing of birth also influenced vaccine exposure. Among infants born from October to November, 74.5% received nirsevimab, while only 52.3% of those born from January to March were exposed to RSVpreF.
Additionally, babies born to mothers under 25 were less likely to receive protection compared to those born to mothers aged 35 or older. Protection rates were highest for babies of Asian mothers at 86.7% and lowest for babies of Black mothers at 70.2%.
The study highlights both progress in protecting infants and areas for improvement. While having two protective options has helped many infants, disparities still exist, particularly among uninsured families. The authors suggest that expanding access to these vaccines is essential to ensure all families can benefit.
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