Herpes Zoster Risk Among Immunocompromised Adults in the United States: A Retrospective Cohort Analysis

OBJECTIVES: Compare herpes zoster (HZ) incidence between United States adults initiating immunosuppressive (IS) medications (IS cohort) and a general cohort of adults without IS medication use (non-IS cohort).

METHODS: This was a retrospective cohort study using October 2015-December 2022 administrative claims data. Adults >18 years old with >1 claim for an IS medication, no HZ vaccination history, and >12 months continuous enrollment prior to the first IS medication fill (index date) were eligible and exact matched by demographic characteristics to adults without evidence of IS medication use. Outcomes included HZ diagnosis and complications, and patients were followed from index until the earlier of HZ diagnosis or vaccination, pregnancy, end of enrollment or study period, or death. HZ incidence rates (IR) were calculated as the number of HZ cases divided by the person-time at risk and presented as the number of HZ cases per 1,000 person-years at risk. Z-tests using robust standard errors in an OLS regression assessed the significance of IR ratios (IRR).

RESULTS: After matching, 517,514 pairs were assessed; demographic characteristics were well-balanced across cohorts, but the baseline prevalence of comorbid conditions was higher among the IS cohort. Over a variable follow-up period, 17,309 and 10,074 HZ events were observed among the IS and non-IS cohorts, respectively. The HZ IR among the IS cohort was 18.08 (95% confidence interval [CI]: 17.81-18.35) compared to 9.80 (95% CI: 9.61-10.00) among matched controls, resulting in an unadjusted IRR of 1.84 (95% CI: 1.80-1.89). Unadjusted IRRs were highest among those aged 18-29 years and declined with increasing age, and a higher proportion of the IS cohort (with HZ) developed post-herpetic neuralgia (21.4% vs. 18.8%, p<0.001).

CONCLUSIONS: IS medication use was associated with elevated HZ risk, reinforcing that measures to prevent HZ should be considered for adults who are or will be immunocompromised. Funding: GlaxoSmithKline Biologicals SA (VEO-000613).