GP consultations for herpes zoster after COVID-19 vaccination: a selfcontrolled cohort study based on electronic health record data from the Netherlands.

Background and objective
Several systematic reviews and meta-analyses have been published with conflicting results on the risk of herpes zoster after coronavirus disease 2019 (COVID-19) vaccination. We aimed to study the risk of herpes zoster after COVID-19 vaccination using electronic health record data of general practices, from a large cohort in the Netherlands.

Methods
Persons aged ≥ 12 years who received at least one COVID-19 vaccination and were registered in the general practice databases of PHARMO and Nivel Primary Care Database were included. This study used a self-controlled design comparing the risk of herpes zoster in the risk period (28 days after COVID-19 vaccination) with the control period. Poisson regression was used to calculate incidence rate ratios, adjusting for severe acute respiratory syndrome coronavirus 2 infection.

Results
There were 2,098,683 COVID-19 vaccinated persons aged ≥ 12 years included, of whom 1,058,646 (50.4%) were female. An increased risk for herpes zoster was found after all the doses grouped together and the third dose of all COVID-19 vaccination (adjusted incidence rate ratio: all doses 1.07, 95% confidence interval [CI] 1.02-1.13 and third dose 1.21, 95% CI 1.05-1.38). After stratification on vaccine type, all doses and the third dose of messenger RNA vaccination (adjusted incidence rate ratio: all doses 1.06, 95% CI 1.00-1.12 and third dose 1.21, 95% CI 1.05-1.40) showed an increased risk.

Conclusions
Our study showed a slight increased risk of herpes zoster when taking into account all doses and all types of vaccines. After stratification on vaccine type, no increased risk of herpes zoster after the primary vaccination series and a slightly elevated risk after the third/booster vaccination with a messenger RNA vaccine were found.