Risk of recurrent herpes zoster in a population-based cohort study of older adults.

Background: There are limited data on zoster recurrence.

Objective: To examine in detail zoster recurrence in a population-based cohort.

Methods: Using data from a large cohort (The 45 and Up Study) with linked medical data (2004-2015), the incidences of first and recurrent zoster were examined by using survival analysis methods.

Results: Over 1,846,572 person-years of follow-up, of 17,413 participants who had a first zoster episode (incidence, 9.43 per 1000 person-years; 95% confidence interval, 9.29-9.57), 675 (3.9%) experienced a recurrence. The mean time between first and recurrent zoster was 2 years for those aged 45-54 years and 3 years for those aged 55 years and older. Among those with a first zoster, the incidence of recurrence was 11.05 (95% confidence interval, 10.24-11.91) per 1000 person-years, and higher recurrence incidence occurred in women compared to men, in younger compared to older participants, and in immunosuppressed compared to nonimmunosuppressed participants. Recurrence appeared lower in the 12 months after zoster onset but then remained consistent at approximately 12.00 per 1000 person-years in the following 8 years.

Limitations: Recurrence may be underestimated because of the use of administrative data for case ascertainment. Potential misclassification of nonimmunosuppressed participants.

Conclusions: Our results support the vaccination of people who have already experienced zoster and underpin the need for additional studies on immunogenicity and vaccine efficacy in these populations.