Key Takeaway:
- Maternal RSV vaccination and infant nirsevimab immunization are safe and produce strong protective antibodies in infants.
- Maternal RSV vaccination shows about 82% effectiveness in preventing infection in pregnant women.
- Multiple studies confirm that both strategies significantly reduce infant RSV hospitalizations and severe respiratory illness.
Six new studies find maternal RSV vaccination and infant immunization with nirsevimab safely reduce respiratory infections, hospitalizations, and complications in mothers and infants, supporting expanded prevention strategies against a leading cause of infant illness.
Studies Confirm Safety, Strong Antibody Protection
Researchers report growing evidence that maternal respiratory syncytial virus vaccination and infant immunization with the monoclonal antibody nirsevimab protect both mothers and babies from severe disease.
A phase four randomized trial led by Emory University followed 181 mother-infant pairs across eight U.S. medical centers. Participants received either maternal vaccination, infant nirsevimab, both interventions, or infant treatment alone.
Interim results published this week in Pediatrics show both approaches, used separately or together, were safe and generated strong neutralizing antibody responses in infants through at least three months after birth.
“Maternal RSV vaccination and infant nirsevimab immunization, administered either alone or sequentially, were safe and provided high antibody levels in infants,” study researchers wrote.
No serious treatment-related adverse events were reported. Most reactions were mild to moderate, and all infants in the trial were born full term.
Maternal vaccination increased antibody levels more than seventeenfold by delivery, with efficient transfer of protective antibodies from mother to infant. Researchers noted most infants likely require only one preventive strategy, though combined use may benefit certain high-risk cases.
The American Academy of Pediatrics currently recommends either maternal vaccination or infant immunization to prevent severe RSV disease.
Maternal Vaccination Shows Protection for Mothers
Separate research published in Vaccine found maternal RSV vaccination also protects pregnant women themselves, offering an additional benefit beyond infant protection.
Investigators analyzed electronic health records of pregnant women tested for RSV between September 2023 and February 2026. After matching 2,434 vaccinated and unvaccinated participants, confirmed RSV infection occurred in zero point five percent of vaccinated mothers compared with two point eight percent of unvaccinated women.
The findings indicate vaccine effectiveness of 82.1% against maternal infection one year after vaccination.
“The preventive effect of RSV vaccination on vaccinated mothers indicates a unique additional benefit compared with infant immunization alone,” the authors wrote.
Researchers said many national policies focus primarily on infant protection because earlier evidence on maternal health benefits was limited.
Multiple Studies Report Fewer Hospitalizations
Four additional studies presented at international meetings and published in medical journals reached similar conclusions about Maternal RSV vaccination and RSV prevention.
A United Kingdom Health Security Agency analysis of nearly 289,000 infants found maternal vaccination reduced infant RSV hospitalization risk by about 81%. Although infants of unvaccinated mothers represented just over half the study population, they accounted for more than 87% of hospitalizations.
Researchers from NYU Health + Hospitals/Elmhurst reported that maternal vaccination or infant nirsevimab significantly lowered infection rates, health care visits, and severe complications among infants in New York.
A nationwide Chilean study published in JAMA Network Open linked nirsevimab to a 79.5% reduction in RSV hospitalizations among high-risk infants, including those born extremely premature or with congenital heart disease.
Another analysis from the Washington State Department of Health and the Centers for Disease Control and Prevention found combined use of maternal vaccination and infant immunization reduced RSV hospitalizations and emergency department visits by 43% among infants seven months or younger during the 2024–25 respiratory season.
Commentary authors Dr. Michael Rajnik and Dr. Martin Ottolini said the evidence suggests longer protection when infants receive nirsevimab, but cautioned that ongoing monitoring is needed to assess rare adverse events and long-term outcomes.
Together, researchers say the expanding body of evidence supports continued use of both preventive strategies to reduce RSV’s global burden, particularly among infants vulnerable to severe lung infections such as bronchiolitis and pneumonia.
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