A large German study finds vaccination not to be a risk factor for multiple sclerosis (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.
Data from over 12,000 MS patients formed the basis of a study by the Technical University of Munich (TUM). It showed that five years before their diagnosis, MS patients were statistically less likely to receive vaccinations than comparator groups. Consequently, there was no positive correlation between vaccinations and the development of MS.
MS is now thought to be a neurological autoimmune disease in which the immune system attacks the brain and spinal cord. It is most likely to occur in young people under the age of 40. Vaccinations are often mentioned as a possible risk factor for MS.
Professor Bernhard Hemmer, director of the neurology department of the TUM hospital, Klinkum rechts der Isar, teamed up with scientists from the medical department and the Bavarian Association of Statutory Health Insurance Physicians (KVB) to analyse a large KVB dataset representative of the general population. The data covered over 200,000 individuals, including more than 12,000 MS patients.
The researchers found that five years before being diagnosed, individuals who went on to develop MS had received fewer vaccinations than those who did not develop MS. This applied to all the vaccines investigated: those against pneumococci, meningococci, mumps, measles, rubella, chickenpox, human papilloma virus (HPV), hepatitis A and B, tick-borne encephalitis (TBE) and influenza. The effect was particularly pronounced in the latter three cases: the control group had received significantly more vaccinations than the individuals who later developed MS.
“The causes are still a mystery. It may be that people perceive the disease long before they are diagnosed and therefore avoid putting additional stress on their immune system. Such effects are in fact evident in our data. Or perhaps the vaccines have a protective effect that prevents the immune system from attacking the nervous system. In any case, given the large volume of data analysed, we can conclusively state that there is no evidence that recent vaccination increases the likelihood of MS or the onset of an initial MS episode,” Alexander Hapfelmeier, lead author of the study, explains.
The researchers also wanted to rule out the possibility that the results might be an underlying effect of chronic diseases in general. They therefore analysed data from two other groups: patients with Crohn’s disease, an inflammatory bowel disorder, and patients with psoriasis, a chronic skin disease. The vaccinations of these patients had also been recorded five years before their diagnosis.
Those patients, however, had received as many vaccinations as the healthy control group. “Thus, the results are not due solely to the presence of a chronic inflammatory disease, but to behaviour specific to MS,” Bernhard Hemmer says, adding: “We already know from other studies that MS sufferers show atypical behaviour and medical history long before they are diagnosed. For example, they are more prone to mental illnesses and also tend to have fewer children. All this clearly indicates that MS is perceived long before any neurological symptoms appear. We therefore need to find suitable markers to diagnose the condition earlier. We see this as one of our most important tasks.”
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.
Alexander Hapfelmeier, Christiane Gasperi, Ewan Donnachie, Bernhard Hemmer