RSV infection in high risk infants and the potential impact of prophylaxis in a UK cohort

BACKGROUND: Bronchiolitis caused by respiratory syncytial virus (RSV) is an important cause of morbidity in ex-premature infants. In a randomised placebo controlled trial monoclonal antibody prophylaxis showed a 55% reduction in relative risk of hospital admission for these high risk infants, against a background incidence of 10.6 admissions per 100 high risk infants. AIMS: To follow a cohort of high risk infants in order to assess hospitalisation rate from RSV and the potential impact of prophylaxis for these patients in a UK local health authority. METHODS: A cohort of high risk infants from a local health authority were followed over the 1998/99 and 1999/2000 RSV seasons. The high risk population was defined as infants who, at the beginning of the seasons studied, were: (1) under 6 months old and born prior to 36 weeks gestation with no domiciliary oxygen requirement; or (2) under 24 months of age and discharged home in supplemental oxygen. All admissions with bronchiolitis during the season were identified. RESULTS: A total of 370 high risk infants were identified for the 1998/99 season and 286 for the following year. Over the two years there were 68 admissions. Significantly more admissions occurred from group 2 infants. RSV was identified in 27 cases (four admissions per hundred high risk infants). Prophylaxis may have saved up to pound 195,134 in hospital costs over the two years, but would have cost pound 1.1 million in drug acquisition costs. CONCLUSIONS: Careful consideration of risk factors is needed when selecting infants for RSV prophylaxis.