Investigation of clinical characteristics as predictive factors for the humoral immune response to the influenza vaccine in patients with rheumatoid arthritis.

The objective of this observational study is to determine characteristics as predictive factors for the humoral immune response to the influenza vaccine in patients with rheumatoid arthritis (RA). Fifty-seven RA patients who visited our department between 2011 and 2012 were recruited for the present study. The anti-influenza antibody titers of a trivalent influenza subunit vaccine (A/California/7/2009 (H1N1)-like strain (A/H1N1 strain), A/Victoria/210/2009 (H3N2)-like strain (A/H3N2 strain), and B/Brisbane/60/2008-like strain (B strain)) were measured at baseline and 4 weeks after the vaccination using the hemagglutination inhibition assay. Associations between the immune response to the influenza vaccine and clinical characteristics such as background, clinical parameters, and "having treatments or not" were examined to determine predictive factors for the immune response to the influenza vaccine. The titers of the three strains were significantly increased in all RA patients after the influenza vaccination. Concerning predictive factors of the immune response, no significant differences were observed in background (age and sex) or clinical parameters (peripheral lymphocyte count, C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, matrix metalloproteinase-3, and disease activity score-28). No significant differences were observed in the titers of anti-influenza antibodies between the treatment (methotrexate, prednisolone, salazosulfapyridine, or tacrolimus) and no-treatment groups. In contrast, there was a significant difference in A/H3N2 strain between the patients with biologics and without biologics. The only factor that affected anti-influenza antibody titers was "having biologics or not"; therefore, the immune response to the influenza vaccine may not be predicted from the viewpoints of background and clinical parameters.