Incidence of complications of herpes zoster in individuals on immunosuppressive therapy: A register-based population study

Herpes zoster (HZ) exposes to alterations of the quality-of-life. HZ is more frequent in immunocompromised individuals, but whether immunosuppression is associated with a higher rate of complications is not well documented. We aimed to assess association between drug-induced immunosuppression and HZ complications.Data from a sample of the French healthcare claims from 01/01/2006 to 12/31/2018 were analyzed. Complicated zoster (CZ) was defined as a hospitalization with a code for HZ or the first-time dispensation of high-dose valacyclovir and specific neuralgia analgesics. Drug-induced immunosuppression was identified through medication dispensation. Risk ratios were calculated to compare incidences in exposed individuals (EI) and non-exposed to immunosuppressive therapy (NEI).We identified 227 and 2838 CZ, accounting for an incidence of 178 per 100,000 person-year (95%CI[154.9-201.1]) and 51.7 per 100,000 person-year (95%CI[49.8-53.6]), in EI and NEI, respectively (risk ratio: 3.44 (95%CI[3.01-3.94]). Mean age was 66 years in both groups. CZ occurred after a median of 11.7 months (IQR[5.3-49.9]) of immunosuppressive therapy. Post-herpetic neuralgia (PHN) lasted at least 3 months in 32.6% and 22.5% of cases in EI and NEI, respectively (p=.01).Drug-induced immunosuppression increases the risk of CZ and exposes to longer-lasting PHN. Figures provided in this study could help guide prophylaxis of HZ.