Palivizumab Adherence and Outcomes in Canadian Aboriginal Children

Aboriginal infants are at risk for serious respiratory infection.

To determine the hazard rate (HR) for respiratory-related illness (RIH) and respiratory syncytial virus (RSV) specific infection hospitalization (RSVH) in Aboriginal versus non-Aboriginal children receiving palivizumab and the effect of adherence on hospitalization.

Palivizumab recipients in the Canadian registry from 2005 to 2014 were included. Adherence was determined by the number of palivizumab doses received during the RSV season and interdose time interval. Adherence proportions between groups were compared by χ test. Cox proportional hazard analysis determined the effect of Aboriginal status and adherence on the risk of RIH and RSVH.

Aboriginal infants comprised 3.6% (701/19,235) of the registry. HR was 1.6 [95% confidence interval (CI): 1.3-2.0, P < 0.001] and 1.2 (95% CI: 0.7-2.2, P = 0.383) for RIH and RSVH. Aboriginal infants were 62.8% and 63.3% adherent with all recommended injections and within stipulated time intervals, respectively, whereas 81.9% (χ = 162.45, df = 1, P < 0.001) and 72.4% (χ = 27.35, df = 1, P = 0.002) of non-Aboriginal infants were correspondingly adherent. Only 39.9% of Aboriginals were perfectly adherent (adherent to total number and injection intervals), compared with 61.7% of non-Aboriginals (χ = 133.89, df = 1, P < 0.001). Even after adjustment for known risk factors, being Aboriginal and nonadherent was associated with higher RIH hazard (HR = 1.4, 95% CI: 1.1-1.8; HR = 1.3, 95% CI: 1.1-1.4, P = 0.004), respectively. Aboriginals nonadherent with interdose intervals had a 2.2-fold increased HR for RSVH (HR = 2.2, 95% CI: 1.2-4.2, P = 0.015).

Prophylaxed Aboriginal infants have a significantly increased RIH and RSVH hazard than non-Aboriginal infants. Improving adherence especially interdose frequency may further reduce hospitalizations in this vulnerable population.