Background A new strain of pandemic influenza emerged in 2009. The Infectious Disease Surveillance Center of Japan reported that almost all influenza occurring from September 2009 to April 2010 in Japan were isolates of the novel pandemic influenza virus A (H1N1) (1). Until now, the efficacy of vaccination against 2009/2010 pandemic influenza in Japanese patients with rheumatoid arthritis (RA) had not been analyzed.
Objectives To investigate the efficacy of vaccination against a novel pandemic influenza and determine the risk factors for attack in Japanese patients with RA in a large observational cohort, Institute of Rheumatology, Rheumatoid Arthritis (IORRA).
Methods Patients with RA who participated in IORRA survey April 2010 were analyzed. Patients were asked to complete a self-questionnaire survey regarding their vaccination status for pandemic influenza and if they had developed the disease. The efficacy of vaccination and pandemic influenza attack rate were calculated, and factors associated with attacks were analyzed by multiple logistic regression analysis. Age, sex, body mass index (BMI), disease activity, physical dysfunction, use of biologics, doses of methotrexate (MTX) and corticosteroid, and vaccination status were used as explanatory variables in the model.
Results A total of 4863 patients (females: 85.6%, mean age: 59.7 years) were analyzed. The percentages of MTX, corticosteroid, and biologics users were 70.5%, 44.8%, and 10.6%, respectively. Approximately one third of patients (1,711, 35.2%) had been vaccinated against influenza, and 148 patients in total developed influenza. Four female RA patients were hospitalized and/or were administered oxygen, and 3 of those patients (75%) had not been vaccinated. The attack rates of vaccinated and unvaccinated patients were 2.2% and 3.5%, respectively. The vaccination odds ratio (OR) for development of influenza was 0.614 (95% confidence interval: 0.414-0.883). Significant risk factors associated with influenza-like illness were no vaccination (OR 1.287, p <0.05) and older age (OR 1.025, p <0.001). BMI, disease activity, disability, MTX and corticosteroid dose, or use of biologics were not associated with development of influenza.
Conclusions This study found that vaccination against pandemic influenza was effective for RA patients in the IORRA cohort. No vaccination and older age were significant risks for influenza attacks in the 2009/2010 season, regardless of disease activity or treatment with corticosteroids, MTX, or biologics.
Weekly reports of influenza virus isolation/detection, Japan. http://idsc.nih.go.jp/iasr/prompt/graph/reffig1.gif
Disclosure of Interest T. Kobashigawa: None Declared, A. Nakajima: None Declared, E. Tanaka: None Declared, E. Inoue: None Declared, A. Taniguchi: None Declared, S. Momohara: None Declared, H. Yamanaka Grant/Research support from: IORRA study is supported by 40 pharmaceutical companies; Asahikasei Kuraray Medical Co.,Ltd. Abbott Japan Co.,Ltd. Asahikasei Pharma Corporation Astellas harma Inc. AstraZeneca K.K. Bristol-Myers Squibb Chugai Pharmaceutical Co.,Ltd. Daiichi Fine Chemical Co.,Ltd. Daiichi Sankyo Co.,Ltd. Dainippon Sumitomo Pharma Co.,Ltd. Eisai Co.,Ltd. GlaxoSmithKline K.K. Hisamitsu Pharmaceutical Co.,Inc. Janssen Pharmaceutical K.K. Japan Tobacco Inc. Kaken Pharmaceutical Co.,Ltd. Kissei Pharmaceutical Co., Ltd. Kowa Pharmaceutical Co.Ltd. Maruho Co.,Ltd. Mitsubishi Chemical Medience Corporation Mitsubishi Tanabe Pharma Corporation Mochida Pharmaceutical Co., Ltd. MSD K.K., Mundipharma K.K. Nippon Chemiphar Co.,Ltd. Nippon Shinyaku Co.,Ltd. Novartis Pharma K.K. Otsuka Pharmaceutical Co.,Ltd. Pfizer Japan Inc. Sanofi-Aventis K.K. Santen Pharmaceutical Co.,Ltd. Sanwa Kagaku Kenkyusho Co.,Ltd. Sekisui Medical Co.,Ltd. Shionogi Co.,Ltd. Taishotoyama Pharmaceutical Co.,Ltd. Takeda Pharmaceutical Company Limited Teijin Pharma Limited Torii Pharmaceutical Co.,Ltd. UCB Japan Co. Ltd. ZERIA Pharmaceutical Co.,Ltd., Consultant for: Abbott, AstraZeneca, Bristol-Myers Squibb, Chugai, Eisai, Janssen, Mitsubishi Tanabe., Pfizer, Takeda, Teijin Pharma, UCB, Speakers Bureau: Abbott, AstraZeneca, Bristol-Myers Squibb, Chugai, Eisai, Janssen, Mitsubishi Tanabe., Pfizer, Takeda, Teijin Pharma, UCB
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