Background: No studies assessing rabies vaccine (RV) tolerability in persons with multiple sclerosis (MS) have been conducted. Given the lack of safety data, RV is recommended essentially only for post-exposure prophylaxis, which is difficult to administer effectively in many rabies-endemic countries. We sought to determine whether RV administration as pre-exposure prophylaxis was associated with MS relapse.
Methods: This retrospective cohort study compared the clinical courses of MS patients in the year before and after rabies vaccination. The year before vaccination was defined as the pre-exposure risk period, the three months thereafter as the exposure-risk period, and the following nine months as the post-risk period. All adult MS patients immunized with RV between 2014 and 2018 and with available medical records in the two-year window were included. The primary outcome was the incidence of symptomatic MS relapse in the exposure-risk period versus the pre-exposure period.
Results: Fifty-five patients received at least one dose of RV. Most (38/55, 69%) were female; mean age was 38.5 years (SD ±9.2). While 21 (38%) patients experienced 24 relapses in the year before vaccination, only three (5%) experienced one relapse each in the post-vaccination exposure-risk period; three others (5%) experienced a total of four relapses in the subsequent post-risk period. The annualized relapse rates in the pre-exposure, exposure-risk, and post-risk periods were 0.44, 0.22, and 0.10, respectively (rate ratio for exposure-risk to pre-exposure periods, 0.509 [95% CI 0.098-1.677]).
Conclusions: In this cohort, rabies vaccination was not associated with clinical MS relapse. Larger, prospective studies are needed to confirm these results.
Keywords: Disease-modifying therapy; Exacerbation; Immunization; Multiple sclerosis; Toxicity.
Copyright © 2021. Published by Elsevier B.V.