Multiple Sclerosis Relapses After Vaccination: A Retrospective Claims Analysis

Introduction
Multiple sclerosis (MS) is an autoimmune, inflammatory condition of the central nervous system, characterized by subacute focal neurological episodes, referred to as MS relapses. As high efficacy disease modifying therapies (DMTs) are increasingly available, the goals of MS treatment have shifted toward a greater focus on health maintenance. Accordingly, individuals with MS are advised to undergo routine vaccinations following the same schedules as the general population. However, vaccination with live attenuated vaccines remains an exception to this general rule, due to concerns that live vaccines can exacerbate MS.

Methods
We conducted a retrospective cohort study of individuals in the real world, using administrative health claims and McNemar’s test, to examine relapse rates in 7,631 individuals with MS in the 60 days before and after several common vaccinations: influenza (flu); tetanus, diphtheria, pertussis (Tdap); human papillomavirus (HPV); live attenuated varicella zoster (VZV); and yellow fever.

Results
Our study found no statistically significant difference in the number of pre- and post-vaccination relapses for individuals who received flu (n=5,550), Tdap (n=2,745), and live VZV vaccines (n=377). There were not enough individuals who received HPV or yellow fever vaccines to perform statistical analysis.

Discussion
While our findings support current clinical practice when recommending routine non-live vaccinations, they are in contrast to prior studies suggesting increased relapse rates after vaccination with live attenuated vaccines. To our knowledge, ours is the first study to examine a cohort larger than 700 individuals, leveraging real-world data in a study of vaccine-associated MS relapses. While further analyses are warranted, our study suggests that live attenuated vaccines do not appreciably increase the risk of MS relapses.