Seropositivity, Risks, and Morbidity From Varicella-Zoster Virus Infections in an Adult PWH Cohort From 2000-2020.

Background: Varicella-zoster virus (VZV) infection disproportionately affects people with HIV (PWH), primarily presenting as herpes zoster. However, VZV seroprevalence, its association with zoster, and clinical outcomes remain understudied in era of modern antiretroviral therapy (ART). We assessed VZV seroprevalence, rates of VZV illness, and associated health care costs in a large cohort of PWH over 20 years. Methods: We performed retrospective chart reviews of patients followed at a regional HIV clinic from January 1, 2000, to December 31, 2020. Serological, immunization, clinical, and costing data were extracted from in-house databases. VZV-related inpatient admissions, emergency department (ED), and urgent care (UC) visits were identified using relevant International Classification of Disease (ICD-10) codes and validated where possible by 2 physicians. Health care utilization costs were adjusted to 2020 Canadian dollars. Results: Of 3006 PWH, VZV serology was available for 2628; of these, 2503 (95.2%) were seropositive. Only 39% of known seronegative patients were subsequently immunized for varicella. During 29 768 years of patient follow-up, 38 hospitalizations and 138 ED/UC visits due to VZV infection were identified. Most occurred in VZV-seropositive PWH <50 years of age (82%) who were unimmunized (99.2%) and not on ART (64.8%). Nearly 25% of hospitalizations were due to laboratory-confirmed VZV meningitis/encephalitis. The average admission cost was CDN$33 001; the total measured cost of VZV illness was CDN$1 258 718. Conclusions: Despite ART and vaccines for chickenpox and shingles, VZV still caused significant costs and morbidity for PWH, occurring at younger ages and often as encephalitis/meningitis. Supporting ART adherence may reduce VZV illness and hospitalization costs in PWH, and the cost-effectiveness of expanding shingles vaccine use warrants further study.