Assessment and optimization of respiratory syncytial virus prophylaxis in Connecticut, 1996-2013

Respiratory syncytial virus (RSV) causes seasonal respiratory infection, with hospitalization rates of up to 50% in high-risk infants. Palivizumab provides safe and effective, yet costly, immunoprophylaxis. The American Academy of Pediatrics (AAP) recommends palivizumab only for high-risk infants and only during the RSV season. Outside of Florida, the current guidelines do not recommend regional adjustments to the timing of the immunoprophylaxis regimen. Our hypothesis is that adjusting the RSV prophylaxis regimen in Connecticut based on spatial variation in the timing of RSV incidence can reduce the disease burden compared to the current AAP-recommended prophylaxis regimen. We obtained weekly RSV-associated hospital admissions by ZIP-code in Connecticut between July 1996 and June 2013. We estimated the fraction of all Connecticut RSV cases occurring during the period of protection offered by immunoprophylaxis ("preventable fraction") under the AAP guidelines. We then used the same model to estimate protection conferred by immunoprophylaxis regimens with alternate start dates, but unchanged duration. The fraction of RSV hospitalizations preventable by the AAP guidelines varies by county because of variations in epidemic timing. Prophylaxis regimens adjusted for state- or county-level variation in the timing of RSV seasons are superior to the AAP-recommended regimen. The best alternative strategy yielded a preventable fraction of 95.1% (95% CI 94.7-95.4%), compared to 94.1% (95% CI 93.7-94.5%) for the AAP recommendation. In Connecticut, county-level recommendations would provide only a minimal additional benefit while adding complexity. Initiating RSV prophylaxis based on state-level data may improve protection compared with the AAP recommendations.