BCG Vaccine for TB Not Linked to MS Risk: Large Canadian Study
Getting the Bacillus Calmette-Guerin (BCG) vaccine to protect against tuberculosis (TB) — an immunization often given to infants and small children in countries where TB is common — does not decrease a person’s risk of developing multiple sclerosis (MS), according to a new study.
“Within a large birth cohort [a group of more than 400,000 adults], we observed no association between either BCG vaccination or age at vaccination and the incidence of [relapsing-remitting MS] RRMS, including pediatric, young adult and adult cases,” the researchers wrote.
The study, “Bacillus Calmette-Guerin vaccination and multiple sclerosis: a population-based birth cohort study in Quebec, Canada,” was published in the European Journal of Neurology.
MS is caused by the body’s immune system accidentally launching an inflammatory attack that damages healthy parts of the brain and spinal cord. Despite advances in treatment, the biological mechanisms that drive the erroneous immune attack in MS remain poorly understood.
While not commonly given in the U.S., the BCG vaccine is one of the most widely used of all current vaccines worldwide, and has been found to protect against some cases of meningitis and TB in children. It broadly is thought to reduce the inflammatory activity of certain parts of the immune system.
Theoretically, reducing inflammation via the BCG vaccine could lessen the risk of MS developing. However, data on the association between a BCG vaccination and MS risk have been scant.
To learn more, a team of scientists in Canada now conducted analyses of databases in Québec. The researchers identified 400,563 people who were born in Quebec in the early 1970s, and had data available for the next several decades. Just under half (44.5%) of these individuals had received the BCG vaccine; most who had received the vaccine had been vaccinated before one year of age.
In the entire group, there were 274 cases of MS diagnosed from 1983 to 1996, and other 1,433 reported from 1997 to 2014.
Statistical analyses broadly showed no links, across several time points, between BCG vaccination and the risk of relapsing-remitting MS. Also, age at vaccination had no apparent effect on MS risk.
“There was no association between BCG vaccination and RRMS in the entire follow-up period,” the researchers wrote.
For non-RRMS types of MS, there were trends in which individuals who had gotten the BCG vaccine appeared more likely to develop MS later in life — though the researchers stressed that including all non-RRMS patients in this one general category makes the meaning of these findings not totally clear.
“An increased risk of later-diagnosis MS in the subgroup of cases with unknown phenotypes was observed, but interpretation is hampered by the probable heterogeneity of MS subtypes represented,” the team wrote. They noted a need for further research into potential connections between BCG vaccination and different subtypes of MS.
In the U.S., the BCG vaccination is used “for only very select people who meet specific criteria and in consultation with a TB expert,” the Centers for Disease Control and Prevention states on its website. However, people born outside of the U.S. may have received this vaccination for TB.