Impact of the Withdrawal of Palivizumab Immunoprophylaxis on the Incidence of Respiratory Syncytial Virus Hospitalizations among Infants Born at 33 to 35 Weeks Gestational Age in the Province of Quebec, Canada (RSV-QC Study)

Introduction: In the Province of Quebec, until 2014 to 2015, infants <6 months of age born at 33 to 35 weeks gestational age (wGA) and classified as moderate to high risk by a Canadian risk scoring tool were included in a palivizumab (PZB) respiratory syncytial virus (RSV) prophylaxis program. We assessed the impact of withdrawal of this indication since 2015 to 2016.

Materials and Methods: We conducted a 4-year observational study in 25 Quebec hospitals. Births at 33 to 35 wGA and lower respiratory tract infection (LRTI)/RSV hospitalizations (H) were identified via discharge databases using International Classification of Diseases-9 or -10 codes. Subjects with other indications for PZB were excluded. Our primary outcome was LRTI/RSV-H, defined as LRTI with laboratory-confirmed RSV or LRTI not virologically tested during RSV season (November–April). Using multivariable regression analyses, we compared the risk of LRTI/RSV-H before (2013–2015; S1/2) and after (2015–2017; S3/4) the change in recommendations. Through chart review and mailed parental questionnaire, we described the clinical course and caregiver burden (health resource utilization; productivity; stressors) of LRTI/RSV-H in 33 to 35 wGA infants.

Results: We identified 6,457 eligible 33 to 35 wGA births in 4 years. LRTI/RSV-H occurred in 105/3,353 (3.13%) infants in S1/2 compared with 130/3,104 (4.19%) in S3/4. Overall, 86.4% were RSV confirmed. In multivariable logistic regression analysis adjusting for sex, wGA, and birth month, S3/4 was significantly associated with LRTI/RSV-H (odds ratio [OR]: 1.36, 95% confidence interval [CI]: 1.04–1.76) but not with RSV-confirmed hospitalization (OR: 1.19, 95% CI: 0.90–1.58). Mean hospital stay duration was 5.6 days; 22.6% required intensive care unit admission and 11.1% mechanical ventilation (mean duration 5.4 days). Prior to admission, subjects had an average of 2.3 emergency room and 2.1 clinic visits for their LRTI. Fathers reported a mean of 28.5 hours missed work because of the hospitalization. Comparing S3/4 to S1/2, the proportion of infants with LRTI/RSV-H classified as moderate to high risk increased from 27.7 to 42.0%.

Conclusion: In a province-wide study, we observed an increase in LRTI/RSV-H among 33 to 35 wGA infants in 2 years after withdrawal of PZB prophylaxis, associated with important, increased health care utilization and parental burden.

Conflict of Interest: G.C. has no conflict of interest or any ongoing financial, professional, or personal relationships with AbbVie except an unrestricted grant for this study and consulting honorarium for the study from AbbVie. M.L. has received an unrestricted grant from AbbVie for this study. E.M. has no bias, affiliation with AbbVie or disclosure to declare; received an unrestricted grant for this study. J.P. has received consulting/speaker fees/honoraria from AbbVie, BD Diagnostics, Cepheid; and research grant funding and contracted research from AbbVie, MedImmune, Janssen, BD Diagnostics. I.D. is an AbbVie employee and holds stock or stock options AbbVie.

Funding: AbbVie Inc. funded this study and participated in the study design, research, analysis, data collection, interpretation of data, reviewing, and approval of the publication.

Keywords: RSV; preterm infant; hospitalization