Palivizumab prophylaxis for respiratory syncytial virus in infants with cystic fibrosis: is there a need?

Respiratory syncytial virus (RSV) infection in cystic fibrosis (CF) infants is associated with significant morbidities. This study's objective is to evaluate the effectiveness and adverse events related to palivizumab (PVZ) in CF infants. Data on respiratory-related illness (RIH) and RSV hospitalizations (RSVH) were collected retrospectively in CF infants aged < 2 years in Alberta, Canada, from 2000 to 2017. Logistic regression models were used to compare the odds of RSVH or RIH in PVZ infants from the Canadian registry of palivizumab (CARESS) versus untreated (UPVZ) infants from Alberta, after adjusting for potential confounders. Illness severity was compared between cohorts using χ ² and t tests. A total of 267 CF infants were included: 183 (PVZ) and 84 (UPVZ). A total of 53.3% were tested for RSV. Fifty-five infants experienced a RIH and 10 had a RSVH. The PVZ cohort experienced similar odds of RSVH but decreased odds of RIH versus UPVZ, adjusting for gestational age, birth weight, birth during RSV peak months, and presence of siblings (Exp(B) = 0.23 [0.11-0.49], p < 0.0005). In RSVH-related subjects, PVZ subjects experienced shorter length of overall stay (LOS; t = 2.39 [df = 7], p = 0.048). In those with a RIH, the PVZ group had shorter overall intensive care unit (t = 3.52 [df = 15], p = 0.003) and hospital LOS (t = 2.11 [df = 52], p = 0.04). No serious adverse events were related to PVZ. The odds of RSVH were similar between groups, but PVZ subjects had decreased odds of RIH. The low number of RSV tests performed may explain the similarity in RSVH rates. Significant differences in LOS may indicate decreased RSVH and RIH illness severity in the PVZ versus UPVZ groups.