Specific Disease-Modifying Therapies are Associated with Increased Risk of Breakthrough COVID-19 Infection in People with Multiple Sclerosis

Dr. Maria Pia Sormani (University of Genoa) and team assessed COVID-19 vaccination data of people living with multiple sclerosis (MS) from 27 Italian MS centres within the Italian Alliance against COVID-19, in order to identify the risk of breakthrough infections among individuals treated with specific disease-modifying therapies (DMTs). The analysis revealed that people with MS, particularly those taking an anti-CD20 medication such as ocrelizumab or fingolimod, continue to be at risk for COVID-19 infection despite being vaccinated. However, the rate of hospitalization due to severe disease course was reduced after vaccination except for people on ocrelizumab.

The study assessed over 19,000 people with MS on DMTs who were vaccinated with at least two doses of an mRNA vaccine between March and December 2021 before the spread of the Omicron variant in Italy. Within eight months after their last vaccine dose, a total of 137 individuals developed breakthrough COVID-19 infections. Researchers found that the rate of breakthrough infection was elevated in those treated with ocrelizumab (2.0% higher) and fingolimod (1.62% higher) compared to other DMTs. Additionally, six individuals on ocrelizumab were hospitalized with one admitted to the ICU but later recovered. The rate of hospitalization among people treated with ocrelizumab was similar to those observed during the pre-vaccination era (16.7% vs 19.4%). There were no deaths reported.

These findings suggest that although the risk of breakthrough COVID-19 infections is higher in vaccinated people with MS who are taking ocrelizumab or fingolimod as compared to other DMTs, they do not tend to develop severe COVID-19 infection outcomes, including death.

These findings serve as a reminder for people with MS who may be at greater risk of worse outcomes from the virus that causes COVID-19 to remain vigilant. Risk factors for hospitalization due to COVID-19 include older age, higher level of physical disability, co-morbidities (i.e. diabetes, high blood pressure, obesity, heart and lung disease, pregnancy), and race and ethnicities (i.e. Black, Hispanic and Indigenous populations). People belonging to high risk groups or living in high risk settings should continue to follow public health guidelines regardless of vaccination status. People with MS who are immunocompromised, including those on anti-CD20 monoclonal antibodies (Ocrevus®, Kesimpta®, Rituxan® and biosimilars), as well as residents in high-risk congregate settings, including long-term care homes who received a three dose primary series may receive a booster dose (fourth dose). Please consult your healthcare provider and public health authority to determine when you are eligible to receive an additional dose or booster as dosing intervals differ across the country. Booster doses have been shown to increase protection in the context of the Omicron COVID-19 variant. There is profound scientific evidence that vaccination, wearing a face mask, social distancing and washing your hands are the best ways to reduce the risk of worse outcomes and slow the spread of the virus.

The MS Society of Canada continues to work with global MS organizations, researchers and healthcare providers to provide up to date COVID-19 guidelines for Canadians living with MS.


A pre-print of the article is available online.