Pregnant women who get vaccinated for respiratory syncytial virus (RSV) cut the odds that their baby is hospitalized for the virus by nearly 70%, according to a study published today in JAMA Network Open.
Before the three-month mark, two to three babies out of every 100 are hospitalized in the United States with RSV. Though a common virus, RSV infections can turn dangerous in babies and small kids who have lower levels of natural immunity. This is especially true for very young infants who can only breathe through their noses and have tiny airways.
If the study’s findings encourage enough pregnant patients to get vaccinated, RSV hospitalizations might become so rare that it could change the face of pediatrics, lead author Anne-Marie Rick, MD, PhD, MPH, a pediatrician at the University of Pittsburgh Medical Center (UPMC) Children’s Hospital of Pittsburgh, told CIDRAP News.
Real-world evidence to help guide patients
The study analyzed health records from the Pittsburgh-based UPMC health system for 274 infants aged 90 days or younger who were hospitalized during the 2023–24 and 2024–25 RSV seasons. Babies were tested for RSV, and the results of those whose mothers received the vaccine during pregnancy were compared with those whose mothers did not.
The researchers found the vaccine was associated with a 68% reduction in RSV hospitalizations for acute respiratory illnesses and a 69% reduction in hospitalizations for lower respiratory tract disease.
These findings closely match the protections produced during clinical trials. This wasn’t a given, said Rick, since the trial volunteers had low-risk pregnancies, while her study drew from the general population, including patients with health complications. Yet, in this real-world setting, the vaccine remained highly effective.
“I’m very pleased,” said Rick. “This is exactly what we hoped to see.”
The results are not surprising, but reassuring, said Malini B. DeSilva, MD, MPH, the co-director of the Pregnancy and Child Health Research Center at the Minnesota-based HealthPartners Institute.
DeSilva, who did not contribute to the study, has previously published research on the RSV virus and the effects of vacation during pregnancy. She said there may be some limitations to applying the findings to a larger population, given that the study was conducted within a single health system.
But overall, she said, the study adds to the growing body of literature that supports recommending the RSV vaccination to pregnant patients.
“Having real-world evidence to reference may also help address vaccine hesitancy or uncertainty among patients,” she said.
Further exploration
Rick and her collaborators plan to continue their analysis for the 2025–26 and 2026–27 RSV seasons, since the volume of illness varies from year to year.
Researchers theorize that the more RSV that’s circulating, the more likely the virus will break through whatever protection the vaccine provides — just as the heavier the hailstorm, the more likely a roof is to sustain. The 2023–24 RSV season had a higher disease burden, yet, as Rick noted, the vaccine still provided a high degree of protection.
In addition to the vaccine, parents now have the option to give their newborns monoclonal antibodies that protect against RSV. The treatment first became available in 2023.
As uptake of both the vaccine and monoclonal antibodies continues to grow, Rick is curious whether parts of the United States will reach a level of herd immunity that could further reduce RSV hospitalizations.
