Herpes Zoster after COVID-19 Infection or Vaccination: A Prospective Cohort Study in a Tertiary Dermatology Clinic

Background. Herpes zoster (HZ) has been observed to occur after COVID-19 infection and vaccination; however, knowledge regarding the demographic data, clinical presentations, and treatment outcomes of HZ is limited. Objective. To compare the demographic data, clinical manifestations, treatments, and outcomes of patients with and without HZ within 14 days of COVID-19 infection or vaccination. Methods. This prospective cohort study involving patients diagnosed with cutaneous HZ was conducted at a dermatology clinic from October 2021 to January 2023. Results. Among a total of 232 patients with HZ, the median age was 62.0 years and 59.1% were female. HZ developed in 23 (9.9%) and four (1.7%) patients after COVID-19 vaccination and infection, respectively. The mean duration from vaccination and the median duration from infection to HZ onset were 5.7 and 8.5 days, respectively. The proportion of female patients was significantly higher in the group of patients with COVID-19 vaccination or infection than in those without such a history ($P$ = 0.035). Patients who developed HZ following the recent COVID-19 infection had a median age of 42.5 years, which was lower than that of the other groups. Dissemination occurred in 8.7% of the patients after COVID-19 vaccination. HZ recurrence was reported in five cases, of which 80% had been vaccinated or infected with COVID-19 during the previous 21 days. All patients had similar durations of antiviral treatment, crust-off time, and duration of neuralgia. Conclusions. HZ after COVID-19 vaccination is more frequently observed in females, while HZ after COVID-19 infection tends to occur in younger patients. Disseminated HZ is more common in patients recently vaccinated against COVID-19. COVID-19 vaccination or infection may trigger recurrent HZ infection.