Skip to content
Home » Vaccines are not linked to multiple sclerosis flare-ups

Vaccines are not linked to multiple sclerosis flare-ups

Over the years, there have been claims that vaccines either caused multiple sclerosis or made the disease worse. Although there was a paucity of evidence supporting these claims, it has persisted, especially among people who push an anti-vaccine narrative.

A large study has been published that examined the links between several vaccines and multiple sclerosis flare-ups. I hate to give away the conclusion so early, but the researchers found none.

As I usually do, I walk the reader through the study methods and then review the results. I think this is an essential study for the safety of vaccines.

person getting vaccinated
Photo by FRANK MERIÑO on

What is multiple sclerosis?

Multiple sclerosis (MS) is a nervous system disease that affects the brain and spinal cord of the patient. The disease damages the myelin sheath, the material that surrounds and protects your nerve cells. This damage slows down or blocks messages between your brain and your body, leading to the symptoms of MS.

These symptoms can include:

  • Visual disturbances
  • Muscle weakness
  • Trouble with coordination and balance
  • Sensations such as numbness, prickling, or “pins and needles”
  • Thinking and memory problems

We do not have good evidence as to what may cause MS. Some genetics researchers suggest it may be an autoimmune disease, which happens when your immune system attacks healthy cells in your body by mistake.

The epidemiology of multiple sclerosis indicates that it affects women more than men, and it often begins between the ages of 20 and 40. Usually, the disease is mild, but some people lose the ability to write, speak, or walk.

Vaccines and multiple sclerosis paper

In a paper published on 5 September 2023 in JAMA Neurology, Lamiae Grimaldi, PharmD, Ph.D., of the Assistance Publique-Hôpitaux de Paris, and colleagues, developed a case-control study to determine if there is a link between vaccines and multiple sclerosis flare-ups.

The researchers utilized the System of National Health Databases registry, which covers some 65 million people in France, which is more than 99% of French residents, along with claims linked to the national hospital discharge database (covering acute, long-term, and emergency visits) and death records. Patients were included if they were diagnosed with a multiple sclerosis flare-up from January 1, 2007, through December 31, 2017, or had a record of care during that period if diagnosed earlier.

Here are the key results:

  • 106,523 MS patients (mean age 43.9 years, 71.8% females) were followed for a mean of 8.8 years.
  • During the overall 11 years of the study, 54.6% of the MS patients were vaccinated, including 45.3% after entry in the MS cohort.
  • The most common vaccination was DTPPHi (for diphtheria, tetanus, poliomyelitis, pertussis, or Haemophilus influenzae) — 30.3% of the MS patients, mainly in those under age 34. The flu (19.2%) and pneumococcus vaccines (7.0%, mainly in those over age 70) were the next most common vaccines for MS patients.
  • There was no increased risk of hospitalization for an MS flare-up in the 60 days after exposure to any vaccine.
  • There was also no increased risk of hospitalization for a multiple sclerosis flare-up in the 60 days after exposure to the DTPPHi, influenza, or pneumococcal vaccines.
  • Because of the small numbers who were vaccinated with the human papillomavirus, hepatitis A, hepatitis B, and measles vaccines, the researchers were unable to determine if they had any effect on the risk of multiple sclerosis flare-ups.

The authors concluded that:

A nationwide study of the French population found no association between vaccination and the risk of hospitalization due to MS flare-ups.


The size and type of this study provide confidence that the results lacked significant confounders or bias. In fact, each of the over 106,000 patients was their own individual clinical trial of these vaccines.

One of the issues is that more research needs to be done to examine any potential links to vaccines that are less frequently given and to repeat this study elsewhere to confirm the results.

Overall, this is an excellent, well-designed study that clearly shows many common vaccines given to adults are not linked to multiple sclerosis flare-ups.


Michael Simpson

Don’t miss each new article!

We don’t spam! Read our privacy policy for more info.

Liked it? Take a second to support Michael Simpson on Patreon!
Become a patron at Patreon!