Effectiveness of Respiratory Syncytial Virus Immunoprophylaxis in Reducing Bronchiolitis Hospitalizations Among High-Risk Infants.

We sought to determine the real-world effectiveness of respiratory syncytial virus (RSV) immunoprophylaxis in a population-based cohort to inform policy. The study population included infants born during 1996-2008 and enrolled in the Kaiser Permanente Northern California integrated health-care delivery system. During the RSV season (November-March), the date of RSV immunoprophylaxis administration and the following 30 days were defined as RSV immunoprophylaxis protected period(s), and all other days were defined as unprotected period(s). Numbers of bronchiolitis hospitalizations were determined using International Classification of Diseases, Ninth Revision, codes during RSV season. We used a proportional hazards model to estimate risk of bronchiolitis hospitalization when comparing infants' protected period(s) with unprotected period(s). Infants who had ever received RSV immunoprophylaxis had a 32% decreased risk of bronchiolitis hospitalization (adjusted hazard ratio = 0.68, 95% confidence interval: 0.46, 1.00) when protected periods were compared with unprotected periods. Infants with chronic lung disease (CLD) had a 52% decreased risk of bronchiolitis hospitalization (adjusted hazard ratio = 0.48, 95% confidence interval: 0.25, 0.94) when protected periods were compared with unprotected periods. Under the new 2014 American Academy of Pediatrics (AAP) guidelines, 48% of infants eligible for RSV immunoprophylaxis on the basis of AAP guidelines in place at birth would no longer be eligible, but nearly all infants with CLD would remain eligible. RSV immunoprophylaxis is effective in decreasing hospitalization. This association is greatest for infants with CLD, a group still recommended for receipt of RSV immunoprophylaxis under the new AAP guidelines.

Vitamin A status of children with a history of respiratory syncytial virus infection in infancy.

In order to extend our earlier observation that children who experience frequent respiratory episodes may benefit from Vitamin A supplementation, 206 children aged 2-7 years who had been hospitalized for bronchiolitis during infancy were randomized into a controlled trial of Vitamin A supplementation. Of these, 149 met the criteria of protocol compliance after 12 months of follow-up. Mean plasma retinol at baseline was 39.2 micrograms/100 ml (s.e.m. = 1.0) and did not increase after 12 months (mean = 36.0 micrograms/100 ml, s.e.m. = 0.7) despite the older age of the cohort. The range observed (11.7-73.9 micrograms/100 ml) included some children at risk of marginal Vitamin A deficiency. Mean plasma retinol levels were 20% lower than those of children experiencing frequent respiratory episodes recorded earlier. Oral supplementation did not change plasma retinol levels, nor did it affect respiratory morbidity.