Risk of herpes zoster in psoriasis patients receiving systemic therapies: a nationwide population-based cohort study

The incidence of herpes zoster in psoriasis patients is higher than in the general population. However, the association between herpes zoster risk and different systemic therapies, especially biologic agents, remains controversial. This study investigated the association between herpes zoster risk and several systemic antipsoriasis therapies. This prospective open cohort study was conducted using retrospectively collected data from the Taiwan National Health Insurance Research Database. We included 92,374 patients with newly diagnosed psoriasis between January 1, 2001, and December 31, 2013. The exposure of interest was the "on-treatment" effect of systemic antipsoriasis therapies documented by each person-quarter. The outcome was the occurrence of newly diagnosed herpes zoster. During a mean follow-up of 6.8 years, 4834 (5.2%) patients were diagnosed with herpes zoster after the index date. Among the systemic antipsoriasis therapies, etanercept (hazard ratio [HR] 4.78, 95% confidence interval [CI] 1.51-15.17), adalimumab (HR 5.52, 95% CI 1.72-17.71), and methotrexate plus azathioprine (HR 4.17, 95% CI 1.78-9.82) were significantly associated with an increased risk of herpes zoster. By contrast, phototherapy (HR 0.76, 95% CI 0.60-0.96) and acitretin (HR 0.39, 95% CI 0.24-0.64) were associated with a reduced risk of herpes zoster. Overall, this study identified an association of both etanercept and adalimumab with an increased risk of herpes zoster among psoriasis patients. Acitretin and phototherapy were associated with a reduced risk.