Combined or individual use of maternal RSVpreF and infant nirsevimab achieved high antibody levels without safety concerns, supporting current RSV prevention strategies.
New data presented at the 2025 IDWeek conference in Atlanta, Georgia, showed that both maternal RSVpreF vaccination and infant nirsevimab immunization—alone or in combination—were safe and produced strong immune responses in infants through 4 months of age.1,2
The prospective, randomized, open-label phase 4 study enrolled 181 mother-infant pairs across 8 sites in the United States. Participants were randomized 1:1:1:1 into 4 groups: maternal RSVpreF vaccination alone; maternal vaccination with infant nirsevimab at birth; maternal vaccination with infant nirsevimab at 3 months; or infant nirsevimab at birth alone.1
Researchers followed participants for safety, tolerability, and the magnitude and durability of RSV-A and RSV-B neutralizing antibodies (nAbs). This interim analysis included follow-up data through 4 months of age.
No related serious adverse events were reported in mothers or infants, and all regimens were well tolerated.1,2
Key findings included:
Maternal RSVpreF vaccination and infant nirsevimab immunization were safe and well tolerated, alone or in combination.
High neutralizing antibody levels were achieved in all infants, regardless of maternal vaccination status.
The study continues to assess long-term immune durability over 12 months.
“Our research reassures new parents that all methods of immunization for RSV are safe and provide high antibody levels to infants, which is especially important as the United States moves into its wave of seasonal respiratory illnesses,” said Christina A. Rostad, MD, director of the Emory Children’s Center Vaccine Research Clinic and presenting author. “The findings add to the large body of evidence that immunizations to prevent RSV are safe and effective.”2
The study, conducted by the Infectious Diseases Clinical Research Consortium with support from the National Institute of Allergy and Infectious Diseases, will continue monitoring participants through 12 months to assess the durability of immune protection in both mothers and infants.
RSV remains the leading cause of lower respiratory tract infections in infants and the most common cause of hospitalization in children under 1 year. Researchers noted these results support current CDC recommendations for maternal RSV vaccination during 32–36 weeks of pregnancy and infant immunization under 8 months of age.1
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