Common adult vaccinations are not associated with an increased risk of developing rheumatoid arthritis, according to research presented this week at the American College of Rheumatology annual scientific meeting in Atlanta.
Rheumatoid arthritis is a chronic disease that causes pain, stiffness, swelling, and limitation in the motion and function of multiple joints. Though joints are the principal body parts affected by RA, inflammation can develop in other organs as well. An estimated 1.3 million Americans have RA, and the disease typically affects women twice as often as men.
"Vaccinations are among the events which have long been postulated as inciting agents for RA, as well as for many other chronic inflammatory diseases of unknown origin," says Camilla Bengtsson, PhD, an epidemiologist at the Institute of Environmental Medicine, Karolinska Institutet in Stockholm, Sweden, and lead investigator in the study.
"In our case-control study including incident cases of newly diagnosed RA, no increased risk of RA following immunization was observed, at least not in the five years prior to disease onset," explains Bengtsson, noting that the study is ongoing. "This indicates that immunological provocation with commonly used vaccines in their present form carries no risk of RA in adults."
The study is based on data from the Epidemiological Investigation of Rheumatoid Arthritis, an ongoing, population-based, case-control study in Sweden designed to investigate associations between genes as well as environmental factors and the risk of developing RA. One of the largest etiological RA studies in the world, EIRA began in 1996 and includes data from more than 8,000 subjects.
For the vaccination study, researchers compared 1,998 participants with RA who were vaccinated within the five years prior to disease onset to 2,252 participants with RA who were not. Each group was matched based on age, gender and place of residence, and all participants were between 18 and 70 years old.
Researchers found no association between vaccinations and the development of RA. Furthermore, they found no association between any specific vaccine (e.g., influenza, tetanus, diphtheria, tick-borne encephalitis, hepatitis A, B, C together, polio, or pneumococcus) and the risk of developing RA.
The study also examined whether vaccinations have a different impact on two smaller groups of participantsthose with ACPA-positive and those with ACPA-negative diseaseand found that the vaccines did not increase the risk of either disease form. ACPA, or anti-citrullinated protein antibodies, are autoantibodies (antibodies directed against one or more of an individuals own proteins) that are frequently detected in the blood of RA patients. ACPAs have proven to be powerful biomarkers of RA and ACPA testing has become a commonly accepted and crucial part of diagnosing the disease.
Finally, the researchers noted that vaccinations did not elevate the risk of RA among participants who smoke and among participants who are carriers of HLA-DRB1 SE allelesa genotypeboth of which are established risk factors of RA.
"Since RA has a hereditary component, our results are reassuring, not only for the population in general, but especially for children and other relatives of patients with RA," Bengtsson says.