Impact of COVID-19 vaccination on the onset of herpes zoster: a narrative systematic review

Abstract The reactivation of herpes zoster (HZ) following COVID-19 vaccination has been increasingly reported in observational cohorts, prompting interest in the potential immunological mechanisms linking vaccine-induced immune modulation and latent varicella-zoster virus (VZV) reactivation. The review aims to summarize epidemiological patterns, highlight potential immunopathological mechanisms, and assess whether the observed associations warrant further mechanistic or preventive research. A systematic review with narrative synthesis was conducted in accordance with PRISMA 2020 recommendations. Comprehensive searches of PubMed, MEDLINE, and Google scholar were performed from January 2020 to March 2024 using combinations of “COVID-19 vaccine,” “herpes zoster,” and “VZV reactivation.” Seven observational studies met the inclusion criteria and were analyzed descriptively without quantitative meta-analysis. The review protocol was registered in PROSPERO (CRD420251010776). Across the seven included studies comprising more than 1.5 million individuals, post-vaccination HZ was uncommon (overall incidence < 0.3%). Most cases occurred within 14–30 days after mRNA vaccination and were mild or self-limiting. Adenoviral and inactivated vaccine recipients showed no consistent increase in risk. A slightly higher frequency was observed among older adults and immunocompromised individuals. No severe systemic complications or long-term sequelae were consistently reported. Current evidence from seven population-based studies supports a transient, low-frequency association between COVID-19 vaccination—particularly mRNA platforms—and HZ reactivation. The phenomenon appears biologically plausible but remains non-causal, and the established benefits of COVID-19 immunization continue to outweigh the minimal risk of VZV reactivation.