A large case-control study on vaccination as risk factor for multiple sclerosis

Objective To investigate the hypothesis that vaccination is a risk factor for multiple sclerosis (MS) by use of German ambulatory claims data in a case-control study.

Methods Using the ambulatory claims data of the Bavarian Association of Statutory Health Insurance Physicians covering 2005–2017, logistic regression models were used to assess the relation between MS (n = 12,262) and vaccinations in the 5 years before first diagnosis. Participants newly diagnosed with Crohn disease (n = 19,296) or psoriasis (n = 112,292) and participants with no history of these autoimmune diseases (n = 79,185) served as controls.

Results The odds of MS were lower in participants with a recorded vaccination (odds ratio [OR] 0.870, p < 0.001 vs participants without autoimmune disease; OR 0.919, p < 0.001 vs participants with Crohn disease; OR 0.973, p = 0.177 vs participants with psoriasis). Lower odds were most pronounced for vaccinations against influenza and tick-borne encephalitis. These effects were consistently observed for different time frames, control cohorts, and definitions of the MS cohort. Effect sizes increased toward the time of first diagnosis.

Conclusions Results of the present study do not reveal vaccination to be a risk factor for MS. On the contrary, they consistently suggest that vaccination is associated with a lower likelihood of being diagnosed with MS within the next 5 years. Whether this is a protective effect needs to be addressed by future studies.