BCG vaccine to prevent tuberculosis not linked to MS risk: Study

Getting the Bacillus Calmette-Guerin (BCG) vaccine to protect against tuberculosis (TB) or having latent (inactive) TB in young adulthood aren’t linked to the risk of developing multiple sclerosis (MS), a Norwegian study found.

The study, “BCG vaccination and multiple sclerosis risk: A Norwegian cohort study,” was published in the Multiple Sclerosis Journal.

MS is an automminue disease that occurs when the immune system mistakenly attacks the myelin sheath, a protective coating around nerve fibers that helps them send signals more efficiently. The loss of myelin leads to progressive nerve fiber degeneration and a range of MS symptoms.

Although generally not recommended for use in the U.S., the BCG vaccine is one of the most widely used vaccines worldwide.

BCG, an attenuated strain of the bacterium Mycobacterium bovis, has been reported to have persistent effects on the immune system that may be relevant to treating or preventing autoimmune diseases. In the U.S., it’s considered only for “people who meet specific criteria and in consultation with a TB expert,” the U.S. Centers for Disease Control and Prevention says on its website.

No link to MS risk established

The study’s objective was “to examine if BCG given in early adulthood decreases MS risk,” the researchers wrote. “A relationship between vaccinations and the risk of developing multiple sclerosis (MS) has not been firmly established,” they wrote.

The scientists analyzed data from a population-based Norwegian TB screening program that took place from 1963 to 1975. The program involved 791,369 individuals, 52% of them women, with a mean age at TB screening of 26.2 years. Some 89% had received the BCG vaccine, at a mean age of 15.6 years.

MS cases were found through the Norwegian MS Registry and Biobank, which started in 2001, and the Norwegian Cause of Death Registry.

A total of 2,862 MS cases, 65% of which were in women, were retrieved. The researchers found no association between MS risk and BCG vaccination, with no differences in the risk of developing MS between BCG-vaccinated individuals and nonvaccinated participants with no signs of TB infection.

The scientists then compared individuals born between 1920 and 1939 to those born between 1940 and 1959. Although the group born in the first period had a lower proportion of vaccinated individuals, fewer MS cases identified with symptom onset, and older age at vaccination, “no clear association with MS risk was seen in any birth cohort category,” the researchers wrote.

Because they wanted to exclude MS cases with disease onset before BCG vaccination, the team then restricted the vaccinated group to individuals who were vaccinated before age 18. Results were not substantially different.

“Neither those BCG vaccinated nor those infected naturally with Mycobacterium tuberculosis differed from the non-vaccinated and uninfected population in terms of MS risk,” the researchers wrote.