Low Risk of Severe COVID-19 in Vaccinated Patients With MS

Patients with multiple sclerosis (MS) who were receiving disease-modifying therapies were found to have rare occurrences of severe COVID-19 if they had received the vaccine, according to a study published in BMJ Neurology Open.¹ The results encourage continued vaccination of patients whose immune systems are affected by treatment.

Patients with MS are more vulnerable to infections due to the condition itself and the treatments that come with managing the condition. Vaccines for COVID-19 rely on antibody levels to produce an immune response, which could affect patients with MS, whose immune systems attack parts of the nervous system.² With early studies showing some difficulties surrounding patients with MS when it comes to outcomes, this study aimed to assess the antibody response, severe COVID-19 outcomes, and breakthrough infections in patients with MS who have been vaccinated.¹

Patients who had received at least 1 dose of a COVID-19 vaccine between June 2021 and December 2023 were invited to join the study. Website advertisements and direct invitations from the Oslo University Hospital and the Norwegian MS Registry and Biobank (NMSRB) were used to recruit participants. Healthy controls were recruited from a study on vaccine response in immunosuppressed individuals.

Comorbidities, height and weight, and lifestyle factors were all self-reported. The NMSRB was used to obtain information on treatment dates for MS and to collect the Expanded Disability Status Scale scores. The Norwegian Immunisation Registry was used to collect data on the vaccine type and dose number for each patient. The Norwegian Patient Registry was used for COVID-19 diagnoses, hospitalizations, ventilation procedures, outpatient visits, and deaths in patients with MS who contracted COVID-19.

Patients were grouped by disease-modifying therapy based on self-report. Hospitalization due to COVID-19 was considered severe disease. All participants received at least 1 of the COVID-19 vaccines. The primary outcome was vaccine-induced seroconversion. Antibody concentrations, breakthrough infection of COVID-19, and hospitalizations due to COVID-19 were the secondary outcomes.

There were 3559 participants who were included in this study. Patients who were not using disease-modifying therapy were significantly older compared with those who were treated. A total of 99.9% of the population had received at least 2 doses of the vaccine, and 95.2% had received 3 doses.

Patients receiving monoclonal antibodies or sphingosine-1-phosphate receptor (S1PR) modulators had reduced rates of seroconversion (43.0% and 48.4%, respectively) after the second dose of the vaccine compared with the other participants who had seroconversions of 88% or higher when using other disease-modifying therapies or no treatment. Those using monoclonal antibodies or S1PRs had seroconversion rates below 60% after the third dose (47.7% and 58.8%, respectively), and other groups exceeded 97%. Median antibody levels were also significantly lower in those using monoclonal antibodies or S1PRs (1 BAU/mL and 4 BAU/mL) compared with healthy controls (6656 BAU/mL)

Overall, 22.3% of the participants had a breakthrough infection, with those diagnosed with MS having a higher incidence if they were receiving monoclonal antibodies (31.2%) or S1PR modulators (23.9%) compared with those receiving other disease-modifying treatments (14.9%) or not receiving treatment (13.0%).

Breakthrough infection was most likely among those receiving monoclonal antibodies (OR, 3.44; 95% CI, 2.49-4.84), followed by those receiving other high-efficacy disease-modifying treatments (OR, 1.88; 95% CI, 1.29-2.77). S1PR modulators were not associated with increased risk of infection, and patients with MS who were not on treatment had reduced risk. Reduced risk of breakthrough infection was independently associated with seroconversion (OR, 0.67; 95% CI, 0.58-0.78).

A total of 1.6% of the participants were hospitalized for COVID-19; those being treated with monoclonal antibodies had the highest rate of admittance at 3.3%. Patients treated with monoclonal antibodies had a higher risk of hospitalization (OR, 8.79; 95% CI, 3.41-32.10).

There were some limitations of this study, including possible underreporting of mild infection, healthy controls predominantly being health care workers, differences in smoking patterns between controls and patients with MS, exclusion of hospital data from 2021, and the lack of data on treatment duration and prior exposure.

“This large, vaccinated cohort of [patients with MS] experienced consistently mild COVID-19 outcomes, even among those receiving immunosuppressive therapies,” the authors concluded. Severe disease was rare regardless of treatment modality, indicating the protection for those with MS looking to be vaccinated.

References

1. Rasmussen TH, Schikora-Rustad S, Lorentzen AR, et al. Low risk of severe COVID-19 in vaccinated people with multiple sclerosis: a nationwide Norwegian study. BMJ Neurol Open. 2026;8:e001556. doi:10.1136/bmjno-2026-001556
2. Multiple sclerosis. Mayo Clinic. November 1, 2024. Accessed March 16, 2026. https://www.mayoclinic.org/diseases-conditions/multiple-sclerosis/symptoms-causes/syc-20350269