An early look at the second dose completion of the recombinant zoster vaccine in Canadian adults: A retrospective database study

Abstract

Background: In 2017, the two-dose recombinant zoster vaccine (RZV) was authorized for use in Canada for the prevention of herpes zoster (HZ) in adults ≥ 50 years of age (YOA), which is administered 2-6 months apart. The National Advisory Committee on Immunization (NACI) states that a 0, 12-month schedule may be considered if flexibility in the timing of the second dose is needed to improve coverage. This retrospective database study evaluated the second-dose completion of RZV in Canada from January 2018 to May 2019.

Methods: Data were obtained from the IQVIA LRx Longitudinal Prescription Database which tracks retail prescriptions of anonymized patients. Patients were followed for 6- or 12-months to evaluate the second dose completion aligned with the licensed RZV dosing schedule and NACI's option for greater flexibility. The primary outcomes were time from first to second dose and the proportion of patients who received the second dose.

Results: In the 6-month (155,747 patients) and 12-month (55,524 patients) analytic cohorts, 65.0% and 74.9% received the second RZV dose within 2-6 months and 2-12 months after the first dose with a truncated mean time of 97.8 days and 109.8 days between doses, respectively. Variation in completion rates was observed across age and geography, but sex, rurality, and pharmacy type did not impact results.

Conclusion: Second dose completion of RZV in Canada is high but suboptimal. Further research to understand the factors influencing second dose timing and completion will be an important next step to improve series completion.

Keywords: Canadian National Advisory Committee on Immunization; Herpes zoster; Longitudinal Prescription Database; Recombinant zoster vaccine.