Background and Aims: The National Multiple Sclerosis Society and other expert organizations recommended that all patients with multiple sclerosis (MS) should be vaccinated against COVID-19. However, the effect of disease-modifying therapies (DMTs) on the efficacy to mount an appropriate immune response is unknown. We aimed to characterize humoral immunity in mRNA-COVID-19 MS vaccinees treated with high-efficacy DMTs. Methods: We measured SARS-CoV-2 IgG response using anti-spike protein-based serology (EUROIMMUN) in 125 MS patients vaccinated with BNT162b2-COVID-19 vaccine 1 month after the second dose. Patients were either untreated or under treatment with fingolimod, cladribine, or ocrelizumab. A group of healthy subjects similarly vaccinated served as control. The percent of subjects that developed protective antibodies, the titer, and the time from the last dosing were evaluated. Results: Protective humoral immunity of 97.9%, 100%, 100%, 22.7%, and 3.8%, was observed in COVID-19 vaccinated healthy subjects ( N = 47), untreated MS patients ( N = 32), and MS patients treated with cladribine ( N = 23), ocrelizumab ( N = 44), and fingolimod ( N = 26), respectively. SARS-CoV-2 IgG antibody titer was high in healthy subjects, untreated MS patients, and MS patients under cladribine treatment, within 29.5–55 days after the second vaccine dose. Only 22.7% of patients treated with ocrelizumab developed humoral IgG response irrespective to normal absolute lymphocyte count. Most fingolimod-treated MS patients had very low lymphocyte count and failed to develop SARS-COV-2 antibodies. Age, disease duration, and time from the last dosing did not affect humoral response to COVID-19 vaccination. Conclusions: Cladribine treatment does not impair humoral response to COVID-19 vaccination. We recommend postponing ocrelizumab treatment in MS patients willing to be vaccinated as a protective humoral response can be expected only in some. We do not recommend vaccinating MS patients treated with fingolimod as a protective humoral response is not expected.

Background: Since vaccination against coronavirus disease 2019 (COVID-19) became available, risks related to vaccinating patients with multiple sclerosis (MS) need to be carefully assessed. Objective: Characterize safety and occurrence of immediate relapses following COVID-19 vaccination in a large cohort of MS patients. Methods: We assessed the safety of BNT162b2 COVID-19 vaccination in adult MS patients. Results: Between 20 December 2020 and 25 January 2021, 555 MS patients received the first dose of BNT162b2 vaccine and 435 received the second dose. There were three cases of COVID-19 infection encountered after the first dose. Safety profile of COVID-19 vaccine was characterized by pain at the injection site, fatigue, and headache. No increased risk of relapse activity was noted over a median follow-up of 20 and 38 days after first and second vaccine doses, respectively. The rate of patients with acute relapse was 2.1% and 1.6% following the first and second doses, respectively, similar to the rate in non-vaccinating patients during the corresponding period. Mild increase in the rate of adverse events was noted in younger patients (18–55 years), among patients with lower disability (Expanded Disability Status Scale (EDSS) ⩽3.0), and in patients treated with immunomodulatory drugs. Conclusion: COVID-19 BNT162b2 vaccine proved safe for MS patients. No increased risk of relapse activity was noted.

Background As immunity against SARS-COV-2 wanes following first and second doses of vaccination, a third dose is administered in several countries around the world. Similarly to the first doses, risks related to vaccination and humoral immune response in patients with multiple sclerosis (MS) need to be assessed. Objective Characterize safety and humoral immune response following the third dose of COVID-19 vaccination in a large cohort of MS patients. Methods We assessed the safety of the third dose of the BNT162b2-COVID-19 mRNA vaccination in adult MS patients and evaluated SARS-CoV-2 IgG response. Results Two hundred and eleven adult MS patients received a third dose of BNT162b2 COVID-19 vaccination. Median follow up time was 66 days from vaccine administration (IQR 54–84). The frequency of any adverse event was 54.5%, with the most common reported adverse events being fatigue, local pain at the injection site, fever and muscle or joint pain. Transient increase in MS symptoms was reported in 3.8% of patients, none of them requiring treatment. The rate of acute relapses treated with IV steroids was 3.3%. In a sub-group of 55 patients, 20 untreated and 35 treated with vaccination-safe disease-modifying treatments, SARS-CoV-2 IgG levels increased 21-fold (median ± SD 21.6 ± 53.05). Conclusions The third dose of COVID-19-BNT162b2 vaccine proved safe for MS patients, with no increased risk of relapse activity. Untreated patients and patients treated with vaccination-safe disease-modifying treatments show significant increase in SARS-CoV-2 IgG levels following the third dose of vaccination.