People diagnosed as having multiple sclerosis (MS) often worry about their symptoms intensifying or returning after receiving a live attenuated vaccine, which can cause vaccine hesitancy. 

But a recent study published in JAMA Network Open found that MS patients can receive live attenuated measles, mumps, and rubella (MMR) and chickenpox (varicella) vaccines without an increased chance of symptom relapse. 

“The results support the administration of these vaccines when indicated and may help reassure clinicians and patients, reducing vaccine hesitancy,” the authors wrote. 

Live attenuated vaccines contain a weakened but still living version of the virus to trigger a robust immune response to help the recipient avoid diseases that the vaccines target.

No increased relapses in vaccinated patients

Researchers at the University of Vic–Central University of Catalonia in Spain led the retrospective cohort study, which looked at 369 adult MS patients. Of the group, 123 people received at least one dose of the live attenuated chickenpox vaccine and/or MMR vaccine, while 246 people received neither, from July 2016 to October 2024. 

The results support the administration of these vaccines when indicated and may help reassure clinicians and patients, reducing vaccine hesitancy.

The investigators detected 36 relapses, with 15 (41.7%) in vaccinated people and 21 (58.3%) in unvaccinated controls. Vaccination did not increase symptom relapses compared with the control group. 

For the study, the researchers considered a relapse an onset of new neurologic signs or exacerbation of existing symptoms lasting a day or more after vaccination, without fever or infection. The relapse must have occurred 30 days or more after any previous relapse. 

Vaccine uptake remains low among MS patients, because some patients and providers fear that live attenuated vaccines could trigger new symptoms or worsen current ones, the authors noted. They hope the findings reassure MS patients of the safety of live attenuated vaccines—especially amid measles outbreaks in the United States and Europe. 

“Demonstrating the safety of MMR vaccination, even in a population traditionally perceived as vulnerable, such as people with MS, is therefore highly relevant for both clinical practice and public health policy,” they wrote.

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