A study led by researchers at the University of Pittsburgh and UPMC published today in JAMA Network Open, a peer-reviewed journal of the American Medical Association, found that vaccination against respiratory syncytial virus (RSV) during pregnancy reduced the risk of hospitalization in young infants by nearly 70%.
This study provides early real-world evidence from U.S. clinical care, showing that administering one dose of the maternal RSV vaccine (RSVpreF vaccine) reduces hospitalization related to RSV in young infants. The results are consistent with findings from RSVpreF vaccine clinical trials. The RSVpreF vaccine was approved by the U.S. Food and Drug Administration in 2023.
"We designed this study to focus on what matters most to families: whether their baby might end up in the hospital," said lead author of the study, Anne-Marie Rick , M.D., Ph.D., assistant professor of pediatrics and clinical and translational science at Pitt School of Medicine and a physician at UPMC Children's Hospital of Pittsburgh and UPMC Magee-Womens Hospital. "The findings show a significant impact for families and for the health system, and it highlights how effective this intervention can be during the most vulnerable months of life."
RSV is the leading cause of hospitalization among infants in the United States. According to the Centers for Disease Control and Prevention (CDC), about 2 to 3 out of every 100 babies younger than 3 months are hospitalized each year due to RSV, with severe cases sometimes requiring oxygen support or mechanical ventilation. Until the RSVpreF vaccine's approval, there was no reliable way to protect healthy newborns from RSV starting at birth.
The study analyzed health records from infants 90 days old or younger who were hospitalized for respiratory illness in western Pennsylvania during the 2023–24 and 2024–25 RSV seasons. Researchers focused on infants who were tested for RSV and compared outcomes between those whose mothers received the vaccine during pregnancy and those whose mothers did not. Infants who received monoclonal antibody protection — a separate RSV prevention option administered after birth — were excluded.
Among infants younger than 3 months, maternal vaccination was associated with approximately 68% effectiveness against hospitalization for respiratory illness caused by RSV and 69% effectiveness against more severe lung infections also caused by the virus.
The results are part of an ongoing four-year study to evaluate the effectiveness of maternal RSV vaccination across multiple seasons. Researchers will continue to follow patients during the 2025–26 and 2026–27 RSV seasons, expanding the analysis to include infants up to 180 days old and assessing how long protection lasts.
"We're continuing to follow patients to understand how well this protection holds over time and across different groups," said Rick. "These kinds of real-world data are critical for helping families, clinicians, and policymakers make informed decisions about how best to protect infants."
Additional Resources
- Published study: Maternal Respiratory Syncytial Virus Prefusion F Vaccination and Acute Respiratory Illness in Infants Link
- More information about Respiratory Syncytial Virus Infection (RSV) Link
- A Parent's Guide to Respiratory Illnesses in Kids Link
Additional authors include Additional authors include Jessica Kerr, M.P.H., Hui Liu, M.S, Guan Yu, Ph.D., Jonathan Hui, M.S., Chung-Chou Chang, Ph.D., Nicole Fazio, D.N.P., Rachael Bieltz, M.P.H., Anjani Ravindra, M.D., Christina Megli, M.D., Ph.D., Arun Jeyabalan, M.D., M.S., Judith Martin, M.D., all from Pitt or UPMC. Jennifer Deese, Ph.D., M.P.H., Sarah Pugh, Ph.D., M.P.H., Divya Patel, M.S., Rong Fan, Ph.D., Jessica E. Atwell, M.P.H., Ph.D., Alejandro Cané, M.D. from Pfizer Inc. and Muhammad Tahir, M.D., from Mercy Catholic Medical Center.
Funding for the study was provided by Pfizer Inc through a collaboration with the University of Pittsburgh. This work was also supported by REDCap and NIH and the Clinical and Translational Sciences Institute at the University of Pittsburgh (UL1-TR-001857).
Conflict of Interest: Rick reported receiving grant support from Pfizer Inc during the conduct of the study and personal fees and serving as site principal investigator (PI) for a vaccine trial from Pfizer Inc outside the submitted work. Liu, Fazio, Ravindra and Jeyabalan reported receiving grant support from Pfizer Inc during the conduct of the study. Martin reported receiving support for vaccine research paid to her institution from Vaxcyte Inc, the NIH, and Leidos Holdings Inc outside the submitted work.
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About UPMC Children's Hospital of Pittsburgh
UPMC Children's Hospital of Pittsburgh is the leading pediatric health care provider in western Pennsylvania, delivering world-class care close to home. Regionally, UPMC Children's offers comprehensive services and specialized programs that meet the unique needs of families throughout our communities. Nationally and globally, UPMC Children's is recognized as a pioneer in advancing pediatric medicine—developing innovative therapies, conducting groundbreaking research, and training the next generation of pediatric specialists. Since 1890, generous community support has fueled the mission to improve the health and well-being of children everywhere. Today, UPMC Children's is consistently ranked among the nation's best, earning recognition in all 11 pediatric specialties by U.S. News & World Report. UPMC Children's commitment to clinical excellence, education, research, and advocacy ensures that children in our region—and around the world—receive the highest standard of care.
About the University of Pittsburgh School of Medicine
As one of the nation's leading academic centers for biomedical research, the University of Pittsburgh School of Medicine integrates advanced technology with basic science across a broad range of disciplines in a continuous quest to harness the power of new knowledge and improve the human condition. Driven mainly by the School of Medicine and its affiliates, Pitt has ranked among the top recipients of funding from the National Institutes of Health since 1998. In rankings released by the National Science Foundation, Pitt is in the upper echelon of all American universities in total federal science and engineering research and development support.
Likewise, the School of Medicine is equally committed to advancing the quality and strength of its medical and graduate education programs, for which it is recognized as an innovative leader, and to training highly skilled, compassionate clinicians and creative scientists well-equipped to engage in world-class research. The School of Medicine is the academic partner of UPMC
