Risk of herpes zoster following mRNA COVID-19 vaccine administration

Background Adverse events following mRNA COVID-19 vaccines, including herpes zoster (HZ), have been reported. We conducted a cohort study to evaluate the association between mRNA COVID-19 vaccination and subsequent HZ at Kaiser Permanente Southern California (KPSC). Research design and methods The vaccinated cohort consisted of KPSC members who received their first dose of mRNA COVID-19 vaccine (mRNA-1273 and BNT162b2) during 12/2020–05/2021 and were matched to unvaccinated individuals on age and sex. Incident HZ cases occurring within 90 days of follow-up were identified by diagnosis codes and antiviral medications. Cox proportional hazards models estimated adjusted hazard ratios (aHR), comparing HZ incidence between the vaccinated and unvaccinated cohorts. Results Cohort included 1,052,362 mRNA-1273 recipients, 1,055,461 BNT162b2 recipients, and 1,020,334 comparators. Compared to unvaccinated individuals, aHR for HZ up to 90 days after the second dose of mRNA-1273 and BNT162b2 was 1.14 (1.05–1.24) and 1.12 (1.03–1.22), respectively. In those aged ≥50 years not vaccinated with zoster vaccine, aHR was also increased after the second dose of mRNA-1273 (1.18 [1.06–1.33]) and BNT162b2 (1.15 [1.02–1.29]) vaccine vs. unvaccinated individuals. Conclusions Our findings suggest a potential increased risk of HZ after a second dose of mRNA vaccines, potentially driven by the increased risk in individuals aged ≥50 years without history of zoster vaccination.