Reduced-Dose Schedule of Prophylaxis Based on Local Data Provides Near-Optimal Protection Against Respiratory Syncytial Virus

Background: Respiratory syncytial virus (RSV) is a major cause of respiratory infections among young children and can lead to severe disease among some infants. Infants at high risk for severe RSV infection receive monthly injections of a prophylactic monoclonal antibody during the RSV season based on national guidelines. We considered whether a reduced-dose schedule tailored to the local RSV season in the continental United States would provide adequate protection.

Methods: Hospitalization data for 1942 counties across 38 states from 1997 to 2009 were obtained from the State Inpatient Databases (Agency for Healthcare Research and Quality). We assessed the timing of RSV epidemics at the county and state levels using a 2-stage hierarchical Bayesian change point model. We used a simple summation approach to estimate the fraction of RSV cases that occur during the window of protection provided by initiating RSV prophylaxis during different weeks of the year.

Results: The timing of RSV epidemic onset varied significantly at the local level. Nevertheless, the national recommendations for initiation of prophylaxis provided near-optimal coverage of the RSV season in most of the continental United States. Reducing from 5 to 4 monthly doses (with a later initiation) provides near-optimal coverage (<5% decrease in coverage) in most settings. Earlier optimal dates for initiating 4 doses of prophylaxis were associated with being farther south and east, higher population density, and having a higher percentage of the population that was black or Hispanic.

Conclusions: A 4-dose schedule of prophylactic injections timed with local RSV epidemics could provide protection comparable to 5 doses and could be considered as a way to improve the cost-effectiveness of prophylaxis.