Respiratory syncytial virus is continuing to spread later into spring than usual, driving most states to extend immunization windows for eligible infants and toddlers. RSV typically peaks in winter and continues into spring, but this year it has remained elevated. Federal data shows that for the third week of March, 7.5% of RSV tests were positive—significantly higher than the 5% test positivity rate at the same time last year.
Immunization is normally recommended through the end of March in most states, but nearly all have extended the immunization period through the end of April. According to data from the Association of Immunization Managers, as of Wednesday, 48 jurisdictions had extended their RSV season through at least April 30. Dr. Susan Kansagra, chief medical officer for the Association of State and Territorial Health Officials, noted that many areas continue to see emergency department visits and hospitalizations lingering into spring, making the extension data-driven and important, as RSV is the leading cause of infant hospitalization.
Two to three out of every 100 infants younger than 3 months are hospitalized with RSV in the US annually, according to the CDC. Already this season, tens of thousands of children have been hospitalized with RSV. To prevent infection in infants and some young children, the American Academy of Pediatrics recommends immunization with monoclonal antibodies. A CDC study published last year found that RSV-associated hospitalization rates among infants up to 7 months old during the 2024-25 season were lower than in previous seasons when these immunizations were not available. This is only the third season that monoclonal antibodies have been available to protect against RSV. Ten jurisdictions, including Florida, Hawaii and Oregon, have year-round RSV seasons or epidemiological data that does not support extending the immunization period.
This article is an AI-assisted summary. All facts and figures are drawn from the original report: https://ktvz.com/health/cnn-health/2026/04/06/rsv-is-still-spreading-prompting-states-to-extend-the-immunization-period/