Effective seroconversion and safety following the pandemic influenza vaccination (anti-H1N1) in patients with juvenile idiopathic arthritis

Objectives: To assess the vaccine response in juvenile idiopathic arthritis (JIA) as an extension of previous observation of immunogenicity and safety of a non-adjuvanted influenza A H1N1/2009 vaccine in a large population of juvenile rheumatic diseases. Moreover, to assess the possible influence of demographic data, disease subtypes, disease activity, and treatment on immunogenicity and the potential deleterious effect of the vaccine in the disease itself, particularly in the number of arthritis and inflammatory markers. Methods: A total of 95 patients with JIA and 91 healthy controls were evaluated before and 21 days after vaccination, and serology for anti-H1N1 was performed by haemagglutination inhibition assay (HIA). Patient and physician visual analogue scales (VAS), Childhood Health Assessment Questionnaire (CHAQ), number of active joints, acute phase reactants, and treatments were evaluated before and after vaccination. Adverse events were also reported. Results: JIA patients and controls were comparable regarding mean current age (14.9 +/- 3.2 vs. 14.6 +/- 3.7 years, p = 0.182). After vaccination, the seroconversion rate was significantly lower in JIA patients compared to controls (83.2% vs. 95.6%, p = 0.008), particularly in the polyarticular subtype (80% vs. 95.6%, p = 0.0098). Of note, JIA subtypes, number of active joints, acute phase reactants, CHAQ, patient and physician VAS, and use of disease-modifying anti-rheumatic drugs (DMARDs)/immunosuppressive drugs were similar between seroconverted and non-seroconverted patients (p > 0.05). Regarding vaccine safety, no deterioration was observed in the number of active joints and acute phase reactants during the study period. Conclusion: Influenza A H1N1/2009 vaccination in JIA induces a lower but effective protective antibody response probably independent of disease parameters and treatment with an adequate disease safety profile.