Systematic Literature Review on the Incidence of Herpes Zoster in Populations at Increased Risk of Disease in the EU/EEA, Switzerland, and the UK

Introduction Older adults and patients with underlying conditions such as immunocompromised (IC) populations (e.g., due to medical conditions or immunosuppressive medication) are at increased risk for herpes zoster (HZ). The first HZ recombinant vaccine for IC patients was approved in 2020. Limited evidence exists to inform decision-makers on HZ incidence in high-risk patients in Europe. This systematic literature review (SLR) assessed HZ incidence across 14 high-risk populations in the European Union/European Economic Area, Switzerland, and the United Kingdom.Methods An SLR (Embase, Medline, 2002-2022, observational studies) was performed to identify HZ incidence (i.e., primary outcomes: rate or cumulative; secondary: relative incidence) in type 1 and 2 diabetes mellitus (DM); chronic obstructive pulmonary disease and asthma; depression; rheumatic disorders (RD); multiple sclerosis (MS); inflammatory bowel diseases (IBD); psoriasis; lupus; human immunodeficiency virus (HIV); solid organ transplantation (SOT); solid organ malignancy (SOM); hematologic malignancy (HM); and stem cell transplantation (SCT).Results Of 776 unique records screened, 59 studies were included (24 reported incidence rate per 1000 person-years; two, cumulative incidence per 1000 persons; and 33, relative incidence). The highest incidence rates were reported for SOT (12.1-78.8) and SCT (37.2-56.1); HM (2.9-32.0); RD (0.41-21.5); lupus (11.0-16.5); IC mixed population (11.3-15.5); HIV/AIDS (11.8-13.0); chronic respiratory diseases (4.7-11.4); SOM (8.8-11.0); IBD (7.0-10.8); DM (4.3-9.4); depression (7.2-7.6); MS (5.7-6.3); and psoriasis (5.3-6.1). In many high-risk populations, HZ incidence was higher for older age groups, women, and some treatments.Conclusions The HZ incidence rate in Europe increased with age and varied across high-risk populations, with high rates for solid organ and stem cell transplants, cancer, and rheumatoid arthritis. Most studies were retrospective with methodological differences affecting generalizability and comparability. Future studies should stratify data by IC population, age, sex, severity, medication, and study timeframe.