Vaccines are not a risk factor for multiple sclerosis (MS), a large data analysis spanning more than 12,250 MS patients in Germany shows.
Fewer vaccinations were given to people who — five years later — would be diagnosed with MS, compared to those who would be diagnosed with other autoimmune disorders or not develop any such disease, it found. Whether vaccines could be protective against MS onset is yet to be determined.
The study “A large case-control study on vaccination as risk factor for multiple sclerosis” was published in the journal Neurology.
As the root cause of MS is not fully understood, and disease mechanisms are said to be immune-mediated, cases where MS was found in a person recently vaccinated raised questions of a possible relationship between the two.
Vaccine safety in people with MS is of great importance. Vaccines are able to prevent some infections known to accelerate MS progression, and to increase the risk of relapses. Except for the yellow fever vaccine, studies have generally found that vaccines are safe, and do not increase the risk of MS onset or relapses.
To collect further evidence on vaccine safety and MS, a team of researchers at the Technical University of Munich (TUM) used a large, nationwide claims database covering more than 200,000 individuals, including 12,262 MS patients.
The researchers found that five years before being diagnosed with MS, these patients went without a number of vaccinations, compared to two groups of people with other chronic autoimmune diseases — Crohn’s, an inflammatory bowel disorder (IBD), and psoriasis, a chronic skin disease — and healthy individuals, all of whom served as controls.
These results were true for 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.
Of note, those who did not go on to develop MS had significantly more vaccinations for influenza and TBE, among all vaccines.
“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,” Alexander Hapfelmeier, the study’s lead author, said in a press release.
“In any case, given the large volume of data analyzed, 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,” Hapfelmeier added.
Data from Crohn’s and psoriasis patients served to rule out the possibility that these observations resulted from underlying effects of chronic immune diseases in general, by confirming that these patient groups received as many vaccinations as those without an autoimmune disorder. Put a different way, people with a record of vaccinations were less likely to have MS, both in relation to people without any autoimmune disease and those who went on to develop Crohn’s or psoriasis.
Rather, results observed in MS patients were not due “solely to the presence of a chronic inflammatory disease, but to behavior specific to MS,” said Bernhard Hemmer, the study’s senior leader.
“We already know from other studies that MS sufferers show atypical behavior 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,” Hemmer said. “We therefore need to find suitable markers to diagnose the condition earlier. We see this as one of our most important tasks.”
The study concluded that vaccination is not “a risk factor for MS. On the contrary, [the results] 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,” the researchers wrote.