Effect of disease-modifying antirheumatic drug therapy on immune response to trivalent influenza vaccine in rheumatoid arthritis

BACKGROUND & OBJECTIVES: Patients with autoimmune rheumatic diseases may be at an increased risk of infection due to disease and use of disease-modifying antirheumatic drug (DMARD) therapy. The present study was done to evaluate the immune response to influenza vaccination in patients with rheumatoid arthritis (RA). METHODS: Fifty one RA patients on stable methotrexate (MTX) therapy (≥15 mg/wk), 51 newly diagnosed DMARD-naïve RA patients and 45 healthy controls received a single dose of inactivated seasonal trivalent influenza vaccine. Blood samples were collected just prior to and four weeks after vaccination. Pre- and post-vaccination antibody titres against the three virus strains were measured by hemagglutination inhibition assay. The impact of age, gender, DMARD treatment and pre-vaccination seroprotection on response to the vaccine was assessed by binary logistic regression analysis for each of the virus strains. RESULTS: Pre-vaccination antibody titres were found to be high in the three study groups for all influenza strains, except for Yamagata strain, the titres for which were low in healthy controls. Trivalent influenza vaccination was found to be safe and stimulated a good antibody response in all study groups. On regression analysis, there was no association of age, gender or MTX therapy with vaccine response, except for Yamagata strain where healthy controls had higher positive immune response (P=0.008; odds ratio – 3.37, 95% confidence interval: 1.36-8.32). INTERPRETATION & CONCLUSIONS: Our results indicated that influenza vaccination was safe in RA patients with no detrimental effect on disease activity. MTX therapy at a dose ≥15 mg/wk did not affect the vaccine response. Presence of high pre-vaccination seroprotective antibody levels in the study population indicates the need for re-examination of recommended annual influenza vaccination in such subgroups of population.