You are absolutely right. Studies have found prednisone > 20 mg/day, use of immunosuppressive therapies, and high lupus disease activity can lower the seroconversion rate to influenza vaccination. Interestingly, in a 2012 study by Borba et al, 555 SLE patients and 170 healthy controls were eval for response to the influenza vaccine. Patients who were on anti-malarial therapy despite concomitant immunosuppression (including prednisone> 20 mg/day), had similar seroconversion rates to patients who were not on immunosuppressants at all (71.4% vs 72%, p=1.00). The authors noted that anti-malarials may restore immunogenicity to vaccinations (1). This idea had been described before in other studies noting improvement in vaccine response for meningococcal and Tetanus-diphtheria vaccines in patients receiving chloroquine. (Ref:1. Rheumatology (Oxford). 2012 Jun;51(6):1061-9.2. J Infect Dis. (1998) 177 (6): 1762-1765.3. Trans R Soc Trop Med Hyg 1983;77:24-31.)