Impact of a Publicly Funded Herpes Zoster Immunization Program on the Burden of Disease in Ontario, Canada: A Population-based Study

Abstract

Background: In September 2009, a live attenuated herpes zoster vaccine (ZVL) became available in Canada. Beginning in September 2016, ZVL was made available to all Ontario residents aged 65-70 through a publicly funded immunization program. We assessed the impact of ZVL availability and its subsequent public funding on herpes zoster burden in this population. Methods: A population-based study of Ontario residents aged 65-70 between January 2005 and September 2018. We used interventional autoregressive integrated moving average models to examine the impact of ZVL market availability and the publicly funded ZVL program on monthly incidence rate of medically attended herpes zoster, defined as an outpatient visit for herpes zoster with a prescription for a herpes zoster antiviral dispensed ≤5 days before or after the visit, or a herpes zoster-related emergency department (ED) visit or hospitalization. In secondary analyses, we examined impacts on any herpes zoster-related ED visits and hospitalizations. Results: We found no association between ZVL market availability and monthly incidence of herpes zoster (P=.32) or monthly rates of ED visits and hospitalizations (P=.88). Conversely, the introduction of publicly funded ZVL reduced the monthly rate of medically attended herpes zoster by 19.1% (from 4.8 to 3.8 per 10000 population; P