Investigation of the safety of live attenuated varicella-zoster virus vaccination in patients with relapse-remitting multiple sclerosis treated with natalizumab: A case series and review of the literature.

Introduction: It is generally recommended to avoid live attenuated vaccines in patients treated with high efficacy disease-modifying treatment (DMT). However, a delay in starting DMT in highly active or aggressive multiple sclerosis (MS) might lead to a significant disability.
Objective: We aimed to report a case series of 16 highly active RRMS patients who received the live-attenuated varicella-zoster virus (VZV) vaccine during treatment with natalizumab.
Methods: This retrospective case series was conducted between September 2015 and February 2022 at the MS Research Center of Sina and Qaem hospital, Tehran, Mashhad, Iran, to identify the outcome of highly active MS patients who received the live-attenuated VZV vaccine on natalizumab.
Results: Two males and 14 females were included in this study, with a mean age of 25.5 ± 8.4-year-old. 10 patients were naïve cases of highly active MS, and six were escalated to natalizumab. The patients received two doses of live attenuated VZV vaccine after a mean of 6.72 cycles of natalizumab treatment. Except for the one who experienced mild chickenpox infection, no serious adverse event or disease activity was evident after vaccination.
Conclusion: While our data do not confirm the safety of the live attenuated VZV vaccine in natalizumab recipients, it highlights the importance of case-by-case decision-making in MS management based on the risk-benefit assessment.
Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest, and no funding has been used for the manuscript.
(Copyright © 2023. Published by Elsevier B.V.)