ObjectiveThe aim of this study was to assess the safety and effectiveness of palivizumab for the prevention of lower respiratory tract infection (LRI) caused by respiratory syncytial virus (RSV) in children with immunocompromised conditions or Down syndrome.MethodsIn this multicenter, post-marketing surveillance study (December 2013 to December 2015), children aged ≤24 months with immunocompromised conditions or Down syndrome (without hemodynamically significant congenital heart disease) receiving palivizumab immunoprophylaxis during two RSV seasons were observed until 30 days after the final palivizumab injection. Safety [adverse events (AEs), serious AEs (SAEs), adverse drug reactions (ADRs), serious ADRs (SADRs)] and effectiveness (frequency, incidence, and duration of hospitalization due to RSV infections) were assessed.ResultsOf 304 patients receiving palivizumab, 167 (54.9%) had immunocompromised conditions, and 138 (45.4%) had Down syndrome; 260 (85.5%) completed palivizumab immunoprophylaxis. The annual mean (±standard deviation) number of doses was 5.3 (±2.4) per season. Overall, 220 AEs occurred in 99 patients (32.6%), including 89 SAEs in 53 patients (17.4%). Of these, 33 AEs in 25 patients (8.22%) were considered ADRs, and 13 ADRs in 11 patients (3.62%) were considered SADRs. In four patients, five SADRs (nephroblastoma and asthma in the same patient, septic shock, device-related infection, and drug-induced liver injury) were previously unreported; however, none were considered drug-related. During the observation period, five RSV infections occurred and two patients required hospitalization.ConclusionPalivizumab was generally safe and effective for the prevention of LRI caused by RSV in newborns, infants, and children with immunocompromised conditions or Down syndrome up to the age of 24 months.Electronic supplementary materialThe online version of this article (doi:10.1007/s40272-017-0264-y) contains supplementary material, which is available to authorized users.

The following sentence, which previously read: ''Newborns, infants, or young children aged 24 months and under who have Down syndrome, and children B 24 months of age without a current hs-CHD if they had experienced persistent respiratory symptoms or regular outpatient treatment due to a respiratory tract infection in previous RSV seasons were also eligible for the study.'' Should read: ''Newborns, infants, or young children aged 24 months and under who have Down syndrome (without a current hs-CHD) were also eligible for the study.''