The changing epidemiology of herpes zoster over a decade in South Korea, 2006-2015.

BACKGROUND

In South Korea, the population is rapidly aging and the prevalence of comorbidities has increased. We investigated longitudinal changes in the herpes zoster (HZ) considering demographic changes and comorbidities in the era of universal single-dose varicella vaccination.

METHODS

We used the population-based database of the National Health Insurance Service in South Korea, with approximately 50 million subscribers during 2006-2015. HZ cases were identified using ICD-10 codes and comorbid conditions were also collected. Incidence rates (IRs) and incidence rate ratios (IRRs) per year were calculated adjusting for age, sex, comorbidities and socioeconomic status, and the temporal trends were examined using segmented negative binomial regression analysis.

RESULTS

Over a decade, the adjusted HZ IR increased significantly from 4.23 to 9.22 per 1000 person-years (adjusted IRR 1.05, 95% confidence interval [CI] 1.04-1.06). However, during 2012-2015, the increasing trends decelerated (adjusted IRR per year 1.01, 95% CI 0.98-1.04) and slope changes differed by age. There was a declining trend in children under 9 years, sustained increase in adults aged 30-39 years, and near-plateau in those aged 50-69 years. Nonetheless, the age distribution of HZ incidence did not change over a decade, with the peak in adults aged 60-79 years. HZ-associated hospitalization rates also increased, with a deceleration in the increasing trends during 2012-2015.

CONCLUSIONS

The HZ burden increased independently of demographic changes and prevalence of comorbidities. However, different trajectories by age group necessitate continuous HZ surveillance for better understanding of these changes, and to provide evidence for development of preventive strategies.