Objective. In SLE, a decreased antibody response on influenza vaccination has been reported. In this study, we assessed whether a booster vaccination could improve antibody responses, as determined by seroprotection rates, in SLE patients. Methods. SLE patients (n ¼ 52) with quiescent disease (SLEDAI 44) and healthy controls (HCs) (n ¼ 28) received subunit influenza vaccine in October-December 2007. After 4 weeks, only SLE patients received a second dose of vaccination. Sera were obtained

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... both vaccinations, and 4 weeks after the second vaccination. At each visit, SLE disease activity was recorded. The haemagglutination inhibition test was used to measure antibody titres. Seroprotection was defined as a titre 540. Results. Following the first vaccination, seroprotection rates and geometric mean titres (GMTs) to each vaccine strain increased in both SLE patients and controls to comparable levels. Seroprotection rates in SLE patients after the first vaccination were 86.5% to A/H1N1, 80.8% to A/H3N2 and 61.5% to the B-strain while GMTs were 92.6, 56.2 and 39.2, respectively. Overall, the booster vaccination did not lead to a further rise of seroprotection rates and GMTs in SLE patients. However, in patients not vaccinated in the previous year, GMT and seroconversion rate to A/H1N1 did rise following the booster vaccination. Both influenza vaccinations did not increase SLEDAI scores. Conclusions. Additional value of a booster influenza vaccination in SLE is limited to patients who were not vaccinated in the previous year.