Rheumatoid arthritis (RA) patients are partially protected by the influenza vaccine 6-10 months after treatment with rituximab. Researchers determined that while the flu vaccine is safe, it is ineffective for RA patients in the first 6 months following rituximab treatment. Previous influenza vaccination in rituximab-treated patients does increase pre- and post-vaccination titers, providing some defense to influenza strains. RA activity was not influenced by administration of the flu vaccine. Complete findings of this study are available in the January 2010 issue of Arthritis & Rheumatism, a journal published by Wiley-Blackwell on behalf of the American College of Rheumatology.
RA, a common autoimmune disease, affects 4.6 million individuals worldwide and more than half of those diagnosed are woman, according to a 2000 report on global incidence by the World Health Organization (WHO). Patients with RA are immunocompromised, meaning their immune systems do not function normally, putting them at increased risk of infection. Due to a compromised immune system, doctors advise RA patients to get vaccinated each year against influenza including the new H1N1 virus.
Sander van Assen, M.D. and colleagues from the University Medical Center Groningen in The Netherlands conducted the largest study to date of the effectiveness of the flu vaccine in RA patients using rituximab. Three groups of patients were enrolled in the study: 23 RA patients using rituximab, 20 RA patients taking methotrexate (MTX), and 29 healthy individuals. Those patients taking rituximab were split into two groups with 11 who received the influenza vaccine 4-8 weeks after treatment with rituximab (early rituximab subgroup), and 12 individuals who were given the flu shot 6-10 months post-treatment with the drug (late rituximab subgroup). Influenza vaccines were administered intramuscularly between October 2007 and January 2008.
Researchers tested geometric mean titers (GMTs) for each group and found they significantly increased for all influenza strains in the MTX-treated group and in healthy controls, but for none of the influenza strains in the rituximab-treated group. In the late rituximab subgroup, a rise in GMT was noted for the A/H3N2 and seasonal A/H1N1 flu strains indicating some recovery of an immune response 6-10 months after treatment by rituximab. Also less rituximab-treated patients reached levels of antibodies needed for protection against influenza for the A/H3N2 and seasonal A/H1N1 when compared with MTX-treated patients, and for the seasonal A/H1N1 when compared with healthy individuals.