Prevalence and risk factors of herpes zoster infection in patients with rheumatic diseases not receiving biologic or targeted therapies

Objectives The objective was to study the prevalence and risk factors of herpes zoster (HZ) infection in patients with rheumatic diseases. Methods Consecutive patients with rheumatic diseases not receiving biologic/targeted DMARDs who attended our rheumatology clinics between March and August 2019 were retrospectively reviewed. Episodes of HZ infection since their first clinic attendance were identified. Laboratory results (total white cell count, neutrophil-to-lymphocyte ratio (NLR), serum albumin, globulin, and creatinine) and use of immunosuppressive medications were compared between those with (preceding infection) and without (preceding last visit) HZ infection. Cox regression analysis was performed to identify factors associated with the first HZ infection in all patients. Results 1,479 patients were studied (88.3% women, age 45.0 +/- 15.8 years). Systemic lupus erythematosus (SLE) (38.7%) and rheumatoid arthritis (28.3%) were the commonest rheumatic diseases. After a follow-up of 14,715 patient-years (9.9 +/- 7.0 years), 219 (14.8%) patients developed 258 episodes of HZ infection, giving an overall prevalence of 1.75/100-patient years. The prevalence rates of HZ were highest in SLE and inflammatory myopathies (2.54 and 2.58 per 100 patient-years, respectively). Patients who experienced HZ reactivation were younger, more likely to have SLE, and had significantly lower serum albumin/globulin levels but higher NLR. Significantly more patients with HZ reactivation were using prednisolone and other immunosuppressive drugs in the visits preceding HZ infection. The cumulative risk of having HZ reactivation at 24 and 48 months was 4.9% and 7.6%, respectively. Cox regression analysis revealed that a diagnosis of SLE, increasing age, higher NLR, use of cyclophosphamide, and increasing doses of prednisolone, azathioprine, hydroxychloroquine and leflunomide were independently associated with HZ infection. Conclusions Reactivation of HZ is fairly common in patients with rheumatic diseases. Underlying SLE, age, neutrophil/lymphocyte ratio, and immunosuppressive therapies are independent risk factors.