Abstract
Introduction: Herpes zoster (HZ) is associated with increased risk of stroke. No study has simultaneously examined the effect of HZ vaccination and antiviral treatment following HZ on risk of acute ischemic stroke (AIS). Methods: We included 35,186 Medicare fee-for-service beneficiaries ≥66 years of age diagnosed with HZ and AIS from 2007-2015. We used a self-controlled case series design to examine the association between HZ and AIS, and estimated the incident rate ratio (IRR) by comparing the incidence of AIS in risk periods (periods following HZ) vs. control periods (rest periods). To minimize confounding by age, we restricted analyses to ±365 days from the HZ index date. To examine effect modification by HZ vaccination and antiviral treatment following HZ, beneficiaries were classified into four groups: (1) no vaccination and no antiviral treatment; (2) vaccination only; (3) antiviral treatment only; and (4) both vaccination and antiviral treatment. We tested for interaction to examine the changes in IRRs across the 4-groups. Results: Among 35,186 Medicare beneficiaries with HZ and AIS, 60.9%, 11.8%, 22.2% and 5.2% were in groups 1 to 4, respectively. IRRs at 0-14, 15-30, 31-90, and 91-180 days following HZ were 1.48 (95% CI 1.37-1.59), 1.31 (1.21-1.42), 1.18 (1.12-1.24), and 1.07 (1.03-1.13), respectively. There was no evidence of effect modification by HZ vaccination and antiviral treatment on AIS (all p-values for interaction across 4-groups IRRs >0.05 with the smallest p=0.129). The pattern of association between HZ and risk for AIS was consistent across age group (66-74yrs, 75-84yrs, and ≥85yrs), sex, and race (non-Hispanic white, non-Hispanic black, Hispanic, other). Conclusions: Risk of AIS increased significantly following HZ, and this increased risk didn’t appear to be modified by HZ vaccination and antiviral treatment following HZ. Primary prevention of HZ by HZ vaccination might be the most effective approach to prevent HZ-associated AIS.
Published Version
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