 This was a non-interventional, prospective, multi-center study with no control group designed to assess the effectiveness of palivizumab in a population of infants at high-risk of serious Respiratory Syncytial Virus RSV illness infants born 35 weeks of gestation and infants 24 months with Bronchopulmonary Dysplasia BPD or Congenital Heart Disease CHD. Participants received immunoprophylaxis during the RSV season, defined as October 2014 through April 2015, in routine clinical settings throughout the Russian Federation. 