Meta-Analysis Explores RSV Incidence and Outcomes in Pregnant Women

A recent meta-analysis published in The Journal of Infectious Diseases highlights the burden of acute respiratory infections associated with respiratory syncytial virus (RSV) during pregnancy in the United States and Europe.

In most healthy adults, RSV either causes no symptoms or feels like a mild cold. However, vulnerable populations like babies, young children, and older people are more likely to become severely ill or hospitalized. Pregnant individuals may also be at higher risk for severe RSV symptoms due to decreased capacity of the lungs and heart. Possible complications of RSV during pregnancy may include pneumonia, sepsis, or preeclampsia.

In August 2023, the FDA approved Abrysvo, an RSV vaccine for use in pregnancy. After a pregnant person receives the RSV vaccine, antibodies pass to the fetus within two weeks. The vaccine aims to help protect babies against severe RSV during the first six months of life.

The new meta-analysis was conducted by corresponding author Harish Nair, Ph.D., professor at the University of Edinburgh along with other researchers from the United States and Europe. The study aimed to determine the proportion of pregnant individuals with acute respiratory infections who tested positive for RSV. The analysis also examined the RSV incidence rate, hospitalizations, deaths, and perinatal outcomes.

The meta-analysis included data from 11 studies spanning from 2010 to 2022. Among a total of 8,126 pregnant individuals included in the study, the proportion with acute respiratory infection testing positive for RSV ranged from 0.9% to 10.7%, with a meta-estimate of 3.4%. The pooled incidence rate of RSV among pregnant individuals was found to be 26.0 per 1000 person-years.

Three of the included studies looked at pregnant individuals with and without RSV and found no difference in the chance of miscarriage, stillbirth, low birth weight, and size for gestational age. Notably, no RSV-associated deaths were reported among the pregnant individuals studied. However, RSV-positive pregnant individuals had higher odds of preterm delivery.

The involved studies were conducted in various countries, including high-income, upper-middle-income, and lower-middle-income regions. Most were cohort studies, with some focusing exclusively on patients receiving care in community settings while others included a combination of community and inpatient settings.

The study's findings suggest that RSV infections in pregnant individuals may have implications for perinatal outcomes, particularly preterm delivery. This research provides more data about the burden of RSV-associated respiratory infections during pregnancy, emphasizing the importance of addressing the risks posed by respiratory infections in this population.

“As countries debate whether to include RSV vaccines in maternal vaccination programs, which are primarily intended to protect infants, this information could be useful in shaping vaccine policy decisions,” the authors wrote in the paper.

Funding for this work comes from the PROMISE project, supported by the Innovative Medicines Initiative 2. This initiative is funded by the European Union's Horizon 2020 program and the European Federation of Pharmaceutical Industries.