Study: Infants born in spring, summer more likely to have RSV in first season
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Key takeaways:
- Children born from May through September generally have the highest risk for first-season medically attended RSV.
- Infants born in March had the lowest risk for first-season medically attended RSV.
Infants born during spring and summer months are the most likely to have a first-season medically attended case of respiratory syncytial virus, according to a study published in the Journal of the Pediatric Infectious Diseases Society.
RSV can cause serious illness, especially in infants and older adults, and is the leading cause of infant hospitalizations in the United States, according to the CDC. A surge of pediatric RSV stretched hospital capacity in 2022, and the virus was part of a winter tripledemic of respiratory diseases that same year, alongside COVID-19 and influenza.
In the U.S., the CDC has recommended two prevention methods for RSV in infants: a maternal vaccine and a monoclonal antibody, which were both introduced last year.
The virus places infants across the comorbidity spectrum at risk, one of the authors of the new study said.
“We have been working on descriptive studies of medically attended RSV among infants in the United States, with a focus on the infant population as a whole,” Jason R. Gantenberg, PhD, assistant professor of the practice of epidemiology at the Brown University School of Public Health, told Healio. “Given the historical seasonal dynamics of RSV, we wanted to understand how an infant's month of birth influences their risk of experiencing a medically attended RSV event, both during their first RSV season and throughout their first year of life.”
Gantenberg and colleagues scanned multiple insurance databases for infants born from July 2016 through February 2020 and looked for the first medically attended RSV event during their first RSV season based on their Census division at birth.
The researchers categorized medically attended events as outpatient, the lowest level of care; emergency department; or inpatient, the highest level of care, based on the recorded locations of respiratory diagnoses occurring near in time to the RSV diagnosis. They classified eligible infants into one of three comorbidity groups: healthy term infants, eligible for palivizumab, and other comorbidities but not eligible for palivizumab.
Ultimately, the researchers found that children born from May through September — just before the RSV season in the fall and winter months — generally had the highest risk for first-season medically attended RSV: between 6% and 10% under the specific definition of RSV and between 16% and 26% when the definition was expanded to include two codes for unspecified bronchiolitis (sentsitive). Infants born in March had the lowest risk.
Proportions of RSV cases classified inpatient ranged from 9% to 54% (specific) and 5% to 33% (sensitive) across birth month and comorbidity group. In the first year of life, the overall risk of RSV was comparable across birth months within each claims base, at 6% to 11% under the specific definition and 17% to 30% under the sensitive.
“Generally, we found that infants born from February through April — that is, born as the respiratory season wanes — had the lowest risk of medically attended RSV during their first season,” Gantenberg said. “All infants have about the same overall risk of experiencing a medically attended RSV event. In other words, infants who make it through their first RSV season without a medically attended event commonly have such an event during their second RSV season.”
Gantenberg is interested in similar analyses conducted in prospective cohorts of infants tested regularly for RSV.
“If we want to know the risk of RSV — rather than medically attended RSV — we need studies capable of detecting RSV in infants outside of health care settings,” Gantenberg said. “I would also be interested seeing future research that characterizes geographic variability in birth month-specific RSV risks, with an eye toward optimizing prevention strategies.”
For more information:
Jason R. Gantenberg, PhD, can be reached at jason_gantenberg@brown.edu.
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