- Objective. To determine whether vaccination of patients with systemic lupus erythematosus (SLE) with influenza virus vaccine is associated with exacerbation of SLE. Methods. The study population comprised 24 patients with SLE who received influenza vaccine (cases group) and 24 other SLE patients who did not receive the vaccine (controls group). The primary outcome measure was the SLE Disease Activity Index (SLEDAI) scores 6 weeks and 12 weeks after vaccination. Secondary outcome measures included: number of SLE flares, defined as any increase in the SLEDAI ≥ 3 points, and activity of renal disease. Repeated measurements MANOVA was used to compare the SLEDAI scores of the cases and controls. Results. All patients were women. The mean age at enrollment into the study was 46.1 and 40.6 years for the cases and controls, respectively. The mean disease duration was 9.1 for the cases and 9.3 years for the controls. SLEDAI scores for the cases and controls were 6.6 and 8.9 at vaccination, 4.9 and 6.8 at Week 6, and 5.1 and 6.7 at Week 12, respectively. The SLEDAI scores of the cases and controls at the 3 different assessments were not statistically different (p = 0.28). However, within each group the decrease in the SLEDAI over time was statistically significant (p = 0.02). Three and 6 flares were observed in the cases and controls, respectively, (p = 0.27) during the 12 weeks of followup. Improvement in the renal disease was observed in the cases and controls. Conclusion. Influenza virus vaccine is safe for patients with SLE. Patients with SLE should be encouraged to receive the vaccine according to the recommendation given by the Immunization Practices Advisory Committee.