Timing of Respiratory Syncytial Virus Prophylaxis

Palivizumab, a monoclonal antibody, is used to prevent serious respiratory syncytial virus (RSV) infections, primarily in infants who are at high risk because of chronic lung disease of prematurity. It confers only passive immunity, so monthly intramuscular doses during RSV season are required. The American Academy of Pediatrics recommends three to five doses — usually between November and March — but in subtropical and tropical areas, the season can extend beyond 5 months. Might prophylactic coverage be better if the dose schedule were specific to each region, based on the dates of recent RSV seasons in that area?

To examine this possibility, investigators from the CDC analyzed data for 1992 to 2007 from 19 laboratories in a sentinel reporting system. Defining the beginning and end of RSV seasons as the first and last consecutive 2-week periods when ≥2 of 10 specimens that were tested each week (or ≥10% of ≥20 tests) were RSV positive, they calculated the median beginning and end dates for 5-, 10- and 15-year periods. The 5-year data (2002–2007) were statistically representative of the 10- and 15-year data and were used in the subsequent analyses.

Compared with the fixed-date method, the median-date method increased the number of seasons during which children were protected from the outset by 15%. The median- and fixed-date schedules were farthest apart at warm weather sites with longer RSV seasons.