CLINICS 2011;66(7):1177-1182 Table 5 - Crude and multivariate adjusted risk ratios (RRs) with 95% confidence intervals for herpes zoster in the SLE patients and non-SLE controls, as stratified by age and gender, during the three-year follow-up period. Crude RR of HZ p-value Adjusted RR of HZ p-value Age, years all ,18 18-24 25-34 35-44 45-54 55-64 .64 Gender Female Male 7.37 (6.75-8.04) 25.81 (18.08-36.84) 11.81 (9.32-14.97) 10.43 (8.46-12.86) 7.40 (6.14-8.93) 4.19 (3.46-5.09) 3.45 (2.54-4.69) 3.65 (2.58-5.17) 7.27 (6.63-7.96) 8.35 (6.33-11.02) ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 ,0.001 2.45 (1.77-3.40) 4.71 (1.41-15.70) 8.78 (3.08-24.97) 3.04 (1.26-7.33) 2.26 (1.06-4.82) 1.79 (0.88-3.65) 2.90 (1.12-7.49) 2.33 (0.79-6.87) 2.10 (1.48-2.99) 7.51 (2.89-19.52) ,0.001 0.012 ,0.001 0.013 0.034 0.108 0.028 0.126 ,0.001 ,0.001 Multivariable regression models adjusted for the variables listed in Tables 1 and 2, including gender, age, insurance level, urbanization level, geographic region, co-morbidities, Charlson co-morbidity index, and prescription medications. data, male SLE patients exhibit a greater level of renal involvement and a worse prognosis19-21 and may have an increased disease severity and a higher risk of HZ infection. In Taiwan, the universal varicella vaccine was introduced for children who were born after mid-2002. However, all of the study subjects in the present study were born before August of 2002; therefore, the relative risk of HZ infection among SLE patients compared with non-SLE patients may Risk of herpes zoster in SLE Chen HH et al. not be influenced by the universal varicella vaccination policy in Taiwan. The finding of a higher risk of HZ in SLE patients raises the issue of whether active immunization should be used in these patients. A randomized controlled trial has shown that zoster vaccine, a live attenuated vaccine, is effective in preventing HZ and post-herpetic neuralgia in the elderly.17 However, there is limited evidence regarding the vaccine’s use in SLE patients.18 Concomitant immuno-suppressive agents may reduce the efficacy of vaccines, and whether there are complications associated with this vaccination in the pathogenesis of SLE remain unclear.18 Further studies are needed to investigate the safety and efficacy of the varicella vaccination in SLE patients. The present study has three advantages. First, the use of an administrative database prevents under-reporting of the number of medical visits.22 Previous studies on the incidence of HZ in SLE patients have mainly used medical record reviews at the selected institutions.2-5,8-9 Second, this nationwide population-based study avoids a selection bias. Third, the present study has adjusted for many important confounding factors, including age, gender, economic status, prescribed medication, and co-morbidities. Although race was not included in these adjustments, greater than 98% of Taiwan’s residents are of Chinese Han ethnicity. This homogenous population makes the results of the present study unlikely to be confounded by race. However, this population also limits the generalization of the study results to other ethnic groups. The present study also has several limitations. First, the accuracy of the diagnoses, which are based on the Figure 1 - The survival curves determined using the Kaplan-Meier survival analysis for herpes zoster among SLE patients and non-SLE patients during the three-year follow-up period. 1181