Hospitalization for Respiratory Syncytial Virus Bronchiolitis in the Palivizumab Prophylaxis Era: Need for Reconsideration of Preventive Timing and Eligibility.

Background: Respiratory syncytial virus (RSV)-related bronchiolitis is a common cause of morbidity in young infants. The recommendations for its passive prevention by palivizumab are currently under intensive debate.

Objectives: To elucidate the optimal prevention strategy by studying the morbidity of RSV disease under the current recommendations for palivizumab prophylaxis in Israel.

Methods: We collected demographic and clinical data of all children hospitalized with microbiologically confirmed RSV bronchiolitis during 2015-2016 at Schneider Children's Medical Center. The seasonality of RSV disease was also studied for the period 2010-2017 in sentinel clinics scattered throughout Israel.

Results: Of the 426 hospitalized children, 106 (25%) had underlying diseases but were not eligible for palivizumab prophylaxis according to the current criteria in Israel. Their course was severe, with a mean hospital stay of 6.7 days and a 12% admission rate to the pediatric intensive care unit (PICU). Palivizumab-eligible children who did not receive the prophylaxis before hospitalization had the most severe course, with 22% admitted to the PICU. More children were diagnosed with RSV disease in October than in March among both hospitalized and ambulatory children; 44% of the palivizumab-eligible hospitalized children were admitted in the last 2 weeks of October, before 1 November which is the recommended date for starting palivizumab administration in Israel.

Conclusions: According to the results of the present study we suggest advancing RSV prophylaxis in Israel from 1 November to mid-October. The precise palivizumab-eligible categories should be reconsidered.