1Celia Oreja-Guevara, 1Judit Díaz-Díaz, 1Elda Alba Suárez, 1Irene Gómez-Estévez, 1Johnny Quezada Sánchez, 1Cristina Bullón-Sánchez, 1Matilde Castro-Hernández, 1Eduardo Martinez-Pérez, 1Silvia O´Connor Pérez, 1Elvira Baos Muñoz

1Hospital Clínico San Carlos, Madrid, Spain


The aim of this study was to study the humoral immune response to SARS-CoV-2 following vaccination in MS patients.

Material(s) and Method(s):

We performed a prospective study including all MS patients receiving one of the approved COVID-19 vaccines since January to September 2021. Demographic characteristics, MS treatments and adverse events reports after COVID-19 vaccination of vaccinated MS patients were collected.

We analyzed the antibody response to SARS-CoV-2 vaccines with a chemiluminescent microparticle immunoassay (CMIA) from Abbot in MS patients with different DMTs at week 3, week 6 and month 3 after the first dose. The positivity cutoff is ≥50 AU/ml (manufacturer defined).

200 Healthy healthcare professionals were the control group.


We analyzed 165 vaccinated MS patients: 106 with Pfizer, 14 with Moderna, 42 with both doses of Astra zeneca and 3 with Jannsen.

The mean age of patients was 45 (range: 21-71) and 46 for the controls.

The most frequent adverse events were pain at injection site, headache and fatigue for 24-48 hours. No differences between MS patients and controls. No increased risk of relapse was noted in the first six months.

120 patients have received both doses of mRNA vaccine.

Overall, mean antibody titers response to SARS-CoV-2 SARS-CoV-2 at three weeks was 7910,3 AU/mL (range 0-74947), at 6 weeks 16347,9 UA/mL (range:0-52380,5) and at 3 months 8182,10 UA/ml (range:0-33752,4) in mRNA vaccinated patients.

By the mRNA vaccinated control group mean antibody titers response to SARS-CoV-2 SARS-CoV-2 at three weeks was 9397 AU/mL and at 6 weeks 18120 UA/mL

Performing a subanalysis of the different DMTs: Only 3 out of 20 patients treated with ocrelizumab developed antibodies. Six vaccinated patients treated with rituximab had no antibody response. Four from 16 patients treated with fingolimod failed to develop a post-vaccination humoral response (< 50 AU/ml). 4 of 5 patients treated with ofatumumab developed have an adequate humoral response.

Patients treated with interferon Beta, glatiramer acetate, teriflunomide, dimethyl fumarate, vaccinated with mRNA vaccines developed a similar post vaccination humoral response than healthy controls.


Most of MS treated patients developed enough antibodies to SARS-CoV-2.

The adverse events on MS patients were similar to the general population. No increase of relapse activity was observed.

Some patients treated with ocrelizumab, rituximab and fingolimod have no developed a humoral response to SARS-CoV-2 vaccination.

Hence we conclude that all approved COVID-19 vaccines are safe in MS patients and effective in most patients. However vaccine strategy in patients treated with anti-CD20 and fingolimod need further studies.