Respiratory syncytial virus prophylaxis in Down syndrome: A prospective cohort study

Background/Objective: Down syndrome (DS) children are at significant risk for respiratory tract (RTI) and respiratory syncytial virus (RSV) infection and hospitalization. We compared hospitalization rates for RTI in DS children aged < 2 years given palivizumab in the RSV season versus a previously published, similar untreated DS birth cohort. Methods: 532 prophylaxed DS children were from the Canadian palivizumab registry (CARESS) between 2005-2012. The untreated group comprised 233 DS children derived from a Dutch, nation-wide birth cohort from 2003-2005. Events during the RSV seasons were counted. Demographics and risk factors were compared using t-test or chi-square where appropriate. Poisson regression analysis was performed to compare incidence rate ratios [95% CI] for both RTI and confirmed RSV hospitalization between the groups while controlling for observation length and known risk factors for severe RSV infection. Results: In total, 31 (23 untreated, 8 treated) RSV-related hospitalizations were documented. The adjusted risk of RSV-related hospitalizations was higher in untreated subjects compa red to palivizumab recipients (incidence rate ratio 3.63 [95% CI: 1.52-8.67], p=0.004). The adjusted risk for hospitalization for all respiratory tract infection (147 events; 73 untreated, 74 treated) was similar (incidence rate ratio untreated versus palivizumab 1.11 [0.80 – 1.55], p=0.53). Conclusions: These results suggest that palivizumab is associated with a 3.6-fold reduction in the incidence rate ratio for RSV-related hospitalization in DS children aged <2 years. A randomized trial is needed to determine the efficacy of RSV immunoprophylaxis in this specific high risk patient population.