Immunogenicity and safety of two doses of a non-adjuvanted influenza A H1N1/2009 vaccine in young autoimmune rheumatic diseases patients

ObjectivesThe aim of this study was to evaluate the immunogenicity and safety of the influenza A H1N1/2009 vaccine in children under 9 years old with autoimmune rheumatic diseases (ARD).MethodsThirty-eight ARD patients and 11 healthy children received two doses of non-adjuvanted influenza A/California/7/2009 (H1N1) virus-like vaccine. Subjects were evaluated before and 21 days after vaccination. Seroprotection (SP) and seroconversion (SC) rates, geometric mean titers (GMT) and factor increases (FI) in GMT were calculated.ResultsMean ages were comparable between patients and controls. Pre-vaccination SP and GMT were similar in patients and controls (p > 0.05). Three weeks after immunization, SP (81.6% vs. 81.8%, p = 1.0), SC (81.6% vs. 90.9%, p = 0.66), GMT (151.5 vs. 282.1, p = 0.26) and the FI in GMT (16.7 vs. 36.3, p = 0.23) were similar in patients and controls, with both groups achieving an adequate response, according to the European Medicines Agency and Food and Drug Administration standards. Analys...