• Phillip J Mease, Christopher T Ritchlin, Richard W Martin, Alice B Gottlieb, Scott W Baumgartner, Daniel J Burge, and James B Whitmore.
• Seattle Rheumatology Associates, 1101 Madison,. Suite 230, Seattle, WA 98104, USA. pmease@nwlink.com
• J Rheumatol. 2004 Jul 1; 31 (7): 1356-61.

ObjectiveTherapeutics used to treat inflammatory diseases, including psoriatic arthritis (PsA), may potentially interfere with normal immune system function. Immune system function can be assessed by evaluating response to vaccination. We assessed the ability of patients with PsA treated with etanercept to produce antibodies in response to pneumococcal antigen challenge.MethodsPatients with PsA (n = 205) were stratified by methotrexate (MTX) use and randomly assigned to receive either placebo or etanercept 25 mg twice weekly by subcutaneous injection. After 4 weeks of treatment with study drug, a 23-valent pneumococcal vaccination was administered. Antibody levels to 5 antigens (9V, 14, 18C, 19F, and 23F) were measured by ELISA before and 4 weeks after vaccination in 184 patients. The proportion (%) of patients with 2- and 4-fold increases in antibody titers was analyzed.ResultsPatients treated with etanercept or placebo had similar responses to the vaccine. A 2-fold increase in titer to at least 2 antigens was achieved by 67% of patients, and a 4-fold increase to at least 2 antigens was achieved by 47% of patients. Approximately 20% of patients in each group failed to show a 2-fold response to any antigens. Logistic regression analysis showed MTX use and age were predictors of a poor response.ConclusionsPatients with PsA treated with etanercept were able to produce antibodies in response to pneumococcal vaccination. Patients receiving MTX had lower mean antibody levels in response to the vaccine. There was no increased risk of poor response with etanercept treatment given alone or with MTX.

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