Varicella zoster virus infections increase the risk of disease flares in patients with SLE: a matched cohort study

OBJECTIVE: To explore whether varicella zoster virus (VZV) infection could increase the risk of disease flares in patients with SLE. METHODS: Patients who had VZV reactivations between January 2013 and April 2018 were included from the SLE database (n=1901) of Shanghai Ren Ji Hospital, South Campus. Matched patients with SLE were selected as background controls with a 3:1 ratio. Patients with SLE with symptomatic bacterial infections of the lower urinary tract (UTI) were identified as infection controls. Baseline period and index period were defined as 3 months before and after infection event, respectively. Control period was the following 3 months after the index period. Flare was defined by SELENA SLEDAI Flare Index. Kaplan-Meier analysis, Cox regression model and propensity score weighting were applied. RESULTS: Patients with VZV infections (n=47), UTI controls (n=28) and matched SLE background controls (n=141) were included. 16 flares (34%) in the VZV group within the index period were observed, as opposed to only 7.1% in UTI controls and 9.9% in background controls. Kaplan-Meier curve revealed that patients with a VZV infection had a much lower flare-free survival within the index period compared with the controls (p=0.0003). Furthermore, after adjusting for relevant confounders including baseline disease activity and intensity of immunosuppressive therapy, Cox regression analysis and propensity score weighting confirmed that VZV infection within 3 months was an independent risk factor for SLE flares (HR 3.70 and HR 4.16, respectively). CONCLUSIONS: In patients with SLE, recent VZV infection within 3 months was associated with increased risk of disease flares.