Relapses after SARS-CoV-2 vaccination in patients with neuromyelitis optica spectrum disorder and multiple sclerosis.

Background: The COVID-19 pandemic outbreak raises the question of whether immunization is recommended for patients with CNS demyelinating diseases. On the one hand, existing studies suggested that SARS-CoV-2 vaccinations are not associated with increased risk of relapse activity. On the other hand, case reports with acute CNS demyelinating disease post vaccination were emerging and raising clinicians' attention.

Methods: In this longitudinal observational study, we included 556 patients with neuromyelitis optica spectrum disorder (NMOSD) and 280 patients with relapsing-remitting multiple sclerosis (RRMS). Each vaccinated patient was matched to two unvaccinated patients according to age, gender, ARR and immunotherapy status, based on propensity score matching model (PSM). The primary outcome is the short- and medium-term risk of relapse, which were evaluated by Kaplan-Meier analysis between groups.

Results: In our cohort, 649 patients (77.6%) have not yet been vaccinated, mainly due to their concerns about relapse. After PSM, 109 vaccinated patients with NMOSD, 218 PS-matched unvaccinated patients with NMOSD, 78 vaccinated patients with RRMS, and 156 PS-matched unvaccinated patients with RRMS were included in the survival analysis to explore the safety of vaccines, with a median of 9-month follow-up. Following the first vaccination dose, 10 patients with NMOSD (9.2%) and four with RRMS (5.1%) experienced an acute relapse. Meanwhile, in the PS-matched unvaccinated group, 15 patients with NMOSD (6.9%) and 12 patients with RRMS (7.7%) presented with an acute relapse. There was no significant difference between the two curves in both NMOSD and RRMS groups over the course of the observation period. There were no significant differences in demographic characteristics, clinical characteristics, and symptoms of relapses between the vaccinated and PS-matched unvaccinated groups. Post vaccination adverse events (ADE) were reported in 39 individuals (20.9%).

Conclusion: Our results indicate that inactivated SARS-CoV-2 vaccines appear safe for patients with CNS demyelinating diseases.