Recurrence Rate of Herpes Zoster and Its Risk Factors: a Population-based Cohort Study

BACKGROUND: Herpes zoster (HZ) is generally thought to occur once in a lifetime and recurrence is considered to be limited to immunocompromised individuals. Although HZ recurrence rates seem to be increasing, there have been few studies exploring these rates in the general population. We investigated the recurrence rate and associated risk factors in the general population. METHODS: We used the population-based samples of the National Health Insurance Service database to identify cases of initial HZ episodes from January 1, 2002 to December 31, 2013. We also followed up on these cases through December 31, 2013 to identify recurrence. RESULTS: Overall, the incidence rate of HZ is 5.1 per 1,000 person years and the recurrence rate is 12.0 per 1,000 person years. There were 2,100 recurrent cases out of 39,441 initial episodes with 4.4 years of the mean follow-up period. We identified significant risk factors for recurrence such as old age (51–70 years) (hazard ratio [HR], 1.447; 95% confidence interval [CI], 1.311–1.598), women (1.476; 1.345–1.619), zoster-related pain (ZRP) longer than 30 days (cases of ZRP lasting 31–90 days [1.200; 1.042–1.383], and ZRP lasting longer than 90 days [2.293; 1.990–2.643]). Concurrent hematologic malignancies (2.864; 1.929–4.251), autoimmune diseases (1.466; 1.252–1.715), dyslipidemia (1.390; 1.263–1.530), and hypertension (1.222; 1.107–1.350) were also significant risk factors. CONCLUSION: Our results suggest that the recurrence of HZ is much more common than generally expected, and that the associated risk factors can play an important role in predicting recurrence.