Immune response to influenza vaccination in rheumatoid arthritis patients taking methotrexate appears to depend most on stopping the next two weekly doses of the drug rather than any effect from the timing of the last dose, new research concludes.
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The new finding, reported in Annals of the Rheumatic Diseases, stems from a post hoc analysis of a randomized, controlled trial that Jin Kyun Park, MD, of Seoul (Korea) National University, and his colleagues had conducted earlier on immune response when patients stopped methotrexate for either 2 or 4 weeks after vaccination. While the main endpoint of that study showed no difference in the improvement in vaccine response with either stopping methotrexate for 2 or 4 weeks and no increase in disease activity with stopping for 2 weeks, it was unclear whether the timing of the last dose mattered when stopping for 2 weeks.
In a bid to identify the optimal time between the last dose of methotrexate and administration of a flu vaccine, Dr. Park and his colleagues conducted a post hoc analysis of the trial, which involved 316 patients with RA receiving methotrexate for 6 weeks or longer to continue (n = 156) or to hold methotrexate (n = 160) for 2 weeks after receiving a quadrivalent influenza vaccine containing H1N1, H3N2, B-Yamagata, and B-Victoria.
The study authors defined a positive vaccine response as a fourfold or greater increase in hemagglutination inhibition (HI) antibody titer. A satisfactory vaccine response was a positive response to two or more of four vaccine antigens.
Patients who stopped taking methotrexate were divided into eight subgroups according to the number of days between their last dose and their vaccination.