Incidence of Herpes Zoster among HIV-infected Patients on Antiretroviral Therapy in Johannesburg, South Africa – Who Should We Vaccinate?

Abstract

Background: Herpes zoster, caused by the varicella zoster virus, is a predominantly dermatologic condition which results in a painful rash in those infected. Commonly seen in the elderly, it can also present as an opportunistic infection associated with HIV infection. Zoster diagnosed early in treatment combined with an increase in CD4 count may be attributed to immune reconstitution inflammatory syndrome (IRIS). Methods: We included all antiretroviral therapy (ART)-naïve patients, ≥18 years old, who initiated treatment between April 2004 and March 2011 at the Themba Lethu Clinic in Johannesburg, South Africa. Incident zoster was defined as any episode occurring after the date of ART initiation. Patients were followed from the date of ART initiation until the date of first zoster diagnosis or death, transfer, loss to follow up (≥3 months late for a scheduled visit), or dataset closure (September 2012). Zoster is described using rates per 1000 person-years and corresponding 95% confidence intervals (CI). A log binomial model was used to estimate risk ratios and 95% CI. Results: 16,261 patients initiated treatment between April 2004 and March 2011 and were followed for 48,982 person-years. 63% were female, median (IQR) age was 36.2 years (31.0-42.7), and median (IQR) baseline CD4 count (cells/µL) was 96 (36-167). Overall, 357 patients (2.2%) had at least one diagnosis of incident zoster recorded and the majority (n=252; 70.6%) were within one year of ART initiation. This corresponded to an overall incidence rate of 7.3/1000 person-years (95% CI: 6.6-8.1) and a one year incidence rate of 18.2/1000 person-years (95% CI: 16.1-20.6). Among the 357 patients with incident zoster, cases were diagnosed in a median (IQR) of 27.1 (11.3-62.0) weeks after treatment initiation and approximately 20% met the case definition for IRIS. In an adjusted model, patients with a low CD4 count (RR 25-49 vs 200+: 1.75; 95% CI: 1.14-2.69) and those with a prior episode of zoster recorded (RR: 2.14; 95% CI: 1.44-3.16) were at increased risk of an incident zoster diagnosis. Conclusions: While only 2% of patients were diagnosed with zoster in this cohort, under-reporting of zoster may have contributed to these low numbers. However, patients with low CD4 counts and those with prior episodes of zoster were at higher risk for a zoster diagnosis. Future research on the use of the zoster vaccine among such patients is needed to determine if the vaccine could be safe andeffective in this cohort.

Conference: CROI conference 2013, Atlanta, USA