MMR, chickenpox vaccines don’t trigger MS relapses, study finds

Measles-mumps-rubella (MMR) and chickenpox (varicella) vaccines do not increase the risk of relapse for people with multiple sclerosis (MS), according to a study involving more than 360 patients.

Both vaccines are recommended for people who are not protected, before starting certain MS treatments that suppress the immune system and can increase the risk of infections. However, because these are live attenuated vaccines — meaning they contain weakened forms of viruses that can trigger a strong immune response — some patients and clinicians have worried they could increase disease activity and lead to relapses in people with MS.

“These findings support [the] administration of live attenuated MMR and varicella vaccines in patients with MS and current recommendations for appropriate immunization before immunosuppressive therapy,” the researchers wrote, adding that the results “may help reassure clinicians and patients, reducing vaccine hesitancy.”

The study, “Live Attenuated Measles-Mumps-Rubella and Varicella Vaccinations and Multiple Sclerosis Activity,” was published in JAMA Network Open.

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Study probes link between live vaccines, MS inflammation

Vaccination is an important part of preventive care in MS, particularly before starting immunosuppressive disease-modifying therapies (DMTs). Current guidelines recommend that people with MS who are not immune to measles, mumps, rubella, or chickenpox through previous infection or vaccination receive appropriate immunization before starting DMTs.

However, concerns have persisted that the immune response triggered by live attenuated vaccines could potentially worsen MS inflammation and trigger relapses. Such concerns may contribute to vaccine hesitancy among both patients and clinicians.

“Despite longstanding concerns and current recommendations, no studies, to our knowledge, have specifically evaluated the inflammatory safety of MMR or varicella vaccines in this population, and robust evidence is needed to guide clinical decision-making,” the researchers wrote.

The team, led by researchers in Spain, analyzed data from 369 people with MS seen at a specialized MS center in Barcelona, who were referred for evaluation of their vaccination status and need for immunization from July 2016 to October 2024.

The analysis covered 123 adults who received at least one dose of an MMR and/or varicella vaccine, as well as 246 matched controls who were not vaccinated because they were already immune.

Participants had a mean age of about 29, and 69.1% of both groups were women. Among vaccinated participants, most (75.6%) received the MMR vaccine, while 21.1% received the varicella vaccine and 3.3% received both.

Before statistical adjustments, vaccinated participants tended to have had more active disease in the previous year, along with greater disability. They were also more likely to be untreated than those in the comparison group.

During one year of follow-up, 36 relapses were recorded. Fifteen (41.7%) involved vaccinated participants, and 21 (58.3%) were unvaccinated individuals. Among vaccinated participants who experienced relapses, 11 (73.3%) had received the MMR vaccine, while three (20%) received the varicella vaccine and one (6.7%) received both vaccines.

After accounting for differences between the groups, researchers found no evidence that vaccination increased the risk of relapse. The analyses showed that receiving an MMR or varicella vaccine was not associated with a clinically meaningful increase in relapse numbers compared with not being vaccinated, meeting the study’s primary goal.

Researchers also examined MRI scans from 50 vaccinated participants who had imaging available both before and after vaccination. They found no increase in inflammatory activity after vaccination. In fact, fewer inflammatory events were detected on scans after vaccination than before it.

The findings remained consistent in additional analyses that accounted for DMT use and when researchers limited the analysis to the first three months after vaccination.

“The results of this study support administration of live attenuated varicella and MMR vaccines in people with MS,” the researchers wrote.