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.