Infants Without Comorbidities Also at Risk for Severe RSV Infection

THURSDAY, Sept. 11, 2025 (HealthDay News) — Comorbidities are seen less often in severe respiratory syncytial virus (RSV) infection in infants younger than 3 months compared with older children, according to a study published online Sept. 9 in The Lancet Regional Health: Europe.

Giulia Dallagiacoma, M.D., from the Karolinska Institutet in Stockholm, and colleagues examined risk factors for RSV-associated severe disease outcomes in children aged 0 to 18 years in a register-based cohort study involving all children born in Sweden between 2001 and 2022.

Overall, 1.7 percent of the 2,354,302 children had an RSV diagnosis; 11.9 percent of these children had severe disease outcomes. The researchers found that the median age of children admitted to the intensive care unit (ICU) was 1.9 months; 41.3 percent had an underlying comorbidity. In the full cohort, the factors most strongly associated with ICU admission or death were birth in winter, small for gestational age, multiple birth, and having siblings aged 0 to 3 years (adjusted hazard ratios, 2.96, 3.91, 3.43, and 2.92, respectively), as well as comorbidities (adjusted hazard ratios, >4). Among children with an RSV diagnosis, similar but attenuated associations were seen. In severe cases, comorbidities were less common in those aged younger than 3 months versus older children (40.3 versus 71.6 percent).

“When shaping treatment strategies, it is important to take into account that even healthy infants can be severely affected by RSV,” Dallagiacoma said in a statement. “The good news is that there is now preventive treatment that can be given to newborns, and a vaccine that can be given to pregnant women.”

Several authors disclosed ties to the biopharmaceutical industry.

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