COVID-19 Vaccination and Herpes Zoster/ Herpes Simplex Reactivation in Tthe Elderly Population: A Pharmacovigilance Analysis

ABSTRACT

Introduction: After the primary infection, the reactivation of both Herpes Simplex viruses (HSV) and Varicella Zoster virus (VZV) is mainly triggered by a secondary immunodeficiency state, either agerelated or iatrogenic, or due to concomitant diseases (e.g., HIV, cancer), especially in the elderly population [1-3]. Indeed, Herpes reactivation has not been commonly associated with immunization and only few cases are described in literature [4]. To date, HSV/VZV reactivation is listed in the Summary of Product Characteristics (SPC) of only one COVID-19 mRNA vaccine [5]. However, even if limited, evidence on a potential correlation between vaccines expressing the SARS-CoV-2 spike (S) glycoprotein and Herpes reactivation is increasing [6]. In Italy, elderly patients represent a population of particular interest for this specific adverse event (AE) since they are currently involved in the 4th booster campaign (which may not be the last one). Objective(s) To investigate the occurrence of Herpes reactivation following COVID-19 vaccination of elderly patients (>= 65 years old) who are going to be frequently vaccinated with this type of vaccines. Method(s) We present Individual Case Safety Reports (ICSRs) concerning COVID-19 vaccination and Herpes reactivation that were collected at our Pharmacovigilance Unit (Milan, Italy) from January 2021. Result(s) So far, 21 ICSRs have been collected, 16 (76%) from ordinary citizens, mainly men (62%) and non-serious. Median age was 74 years (min-max 65-89). Further analyses are ongoing. Conclusion(s) Cases of interest were of non-serious nature and the estimated incidence of pharmacovigilance reports concerning Herpes reactivation was non-significant compared to the total number of Italian citizens who usually suffer from these conditions and to those who have been vaccinated. The vaccination remains strongly recommended. However, it is crucial that clinicians continue to monitor and report all suspected AEs in order to better characterize the safety profile of vaccines.