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COVID-19 Vaccine Boosters and Additional Doses


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Last updated: August 25, 2021

Those age 18 and older who have received two doses of an mRNA vaccine [Pfizer BioNTech (Comirnaty) or Moderna] will be eligible for a COVID-19 vaccine booster starting in September. The booster is expected to be available eight months after their second dose of the mRNA vaccine. People with MS age 12* and older who are fully vaccinated with an mRNA vaccine may be eligible to receive an additional vaccine dose now. Talk with your healthcare provider to determine the best time to get your additional dose.

* Only the Pfizer BioNTech (Comirnaty) vaccine is authorized for age 12 and older and approved for age 16 and older.

The following guidance is based on available data from studies and expert consensus opinion.

Ask an MS Expert: Vaccine Use in MS and COVID-19 Update

Ask an MS Expert: Vaccine Use in MS and COVID-19 Update

Recorded on August 20, 2021

People with MS may be eligible for an additional dose now

The U.S. Food and Drug Administration (FDA) has authorized an additional COVID-19 vaccine dose for people who are not expected to have normal and/or adequate immune responses after two doses of the vaccine. Studies of the COVID-19 vaccine responses in MS have shown a reduced or absent antibody response to the vaccine among those who use certain disease modifying therapies (DMTs).

People with MS using the following DMTs may benefit from an additional dose:
  • sphingosine 1-phosphate receptor modulators (Gilenya, Mayzent, Zeposia, Ponvory),
  • alemtuzumab (Lemtrada) and
  • anti-CD20 monoclonal antibodies (Ocrevus, Kesimpta, Rituxan and biosimilars)
Like other medical decisions, the decision to get an additional dose is best made in partnership with your healthcare provider. Talk to your MS healthcare provider to determine what is best for you.

Boosters are different than an additional dose

An additional dose is intended to improve immunocompromised people’s response to their first and second dose of vaccine. A booster dose is given to people when the immune response to the first and second dose is likely to have waned over time. An additional dose can be administered as soon as 28 days following your second vaccine injection. Boosters are expected to be available eight months after the second dose of an mRNA vaccine.

Timing vaccines with DMTs

A recent study of people with MS who use B cell depleting DMTs showed a better antibody response when the vaccine was administered three months or more after the last dose of DMT. Work with your MS healthcare provider to determine the best time to get your booster and use our vaccine timing considerations in that discussion.

J&J vaccine

Current data does not support the use of an additional dose after receiving a J & J COVID-19 vaccine in immunocompromised people. FDA and Centers for Disease Control and Prevention (CDC) are actively working to provide guidance on this issue. The National MS Society’s COVID-19 Vaccine Advisory Group will continue to monitor this and update our guidance as needed.

Having MS does not make you immunocompromised, but some DMTs do reduce your immune responses to vaccines

Having MS does not compromise your immune system. Current evidence shows that having MS does not make you more likely to develop COVID-19 or to become severely ill or die from the infection than the general population. However, some DMTs used to treat MS do alter your immune system and certain groups of people with MS are more susceptible to having a severe case of COVID-19, including people taking B cell depleting DMTs.

COVID-19 antibodies in people with MS

Antibody tests are helpful to determine if someone may have been exposed to the SARS-CoV-2 virus (the virus that causes COVID-19), but antibody tests are not recommended by the FDA to determine immunity or protection against COVID-19. Learn more from the FDA.

An additional dose of the mRNA vaccines produces more robust immune responses against the SARS-CoV2 virus (the virus that causes COVID-19). These responses can include an increase in antibodies (produced by B cells) as well as an increase in the immune cellular responses (T cells)—both of which offer protection from serious illness due to COVID-19.

People who lack B cells, such as those on B cell depleting therapies, may have reduced or even absent antibody responses to the additional dose as well, though other aspects of their vaccine response (T cells) are likely to be increased. A recent study of people with MS who had a reduced or absent antibody response to the COVID-19 vaccine showed increased T cell responses. This finding shows the importance of vaccination for all people with MS regardless of the anticipated antibody response.

Vaccine side effects

Data from currently available studies indicate that the side effects of the third dose of mRNA vaccine [Pfizer BioNTech (Comirnaty) or Moderna] were similar to prior doses. Any vaccine can cause side effects, including a fever. A fever can make MS symptoms worse temporarily, but they should return to prior levels after the fever is gone. Even if you had side effects after the first or second dose, it’s important to discuss a dose with your healthcare provider. 

Treating and preventing COVID-19

The FDA recommends that immunocompromised individuals discuss monoclonal antibody treatment options with their health care provider should they contract or be exposed to COVID-19. One authorized product includes use for preventative (prophylaxis) treatment after being exposed to COVID-19; however, this product is not a substitute for vaccination. Learn more about this treatment and MS.   
Science has taught us the best protection against COVID-19 infection is a combination of vaccination and physical protection measures. Until more is learned about the protection of those using immunocompromising DMTs, continue to take precautions against COVID-19, like mask wearing, hand washing, physical distancing and avoiding crowds and poorly ventilated indoor spaces. Also, encourage those close to you to get vaccinated.

How to get an additional dose

Each state offers the additional dose at different locations and what is required to show proof of your eligibility to receive an additional dose varies. Visit to learn more and find a location near you.

Experts consulted in the development of this guidance

MS neurologists and experts

  • Nancy Sicotte, MD, FAAN—Chair, National MS Society’s National Medical Advisory Committee, Cedars-Sinai Medical Center, USA
  • Brenda Banwell, MD— Chair of MS International Federation International Medical and Scientific Advisory Board (IMSB) – University of Pennsylvania, USA
  • Amit Bar-Or, MD, FRCPC—President, International Society for Neuroimmunology - University of Pennsylvania, USA
  • Jorge Correale, MD-- Raul Carrea Institute for Neurological Research, FLENI, Buenos Aires, Argentina
  • Anne Cross, MD, FAAN—Washington University and Secretary of Board of Governors of the Consortium of MS Centers, USA
  • Jaime Imitola, MD, FAAN—University of Connecticut, UConn Health, USA
  • Dorlan Kimbrough, MD—Duke University, USA
  • Avindra Nath, MD—National Institutes of Health/National Institutes of Neurological Disorders and Stroke, USA
  • Scott Newsome, DO, MSCS, FAAN, FANA—Johns Hopkins University and President of the Board of Governors of the Consortium of MS Centers, USA
  • Penny Smyth, MD, FRCPC—University of Alberta, Canada
  • Rachael Stacom, MS, ANP-BC, MSCN—Independence Care System, USA
Staff from MS Partner Organizations
  • Julie Fiol, RN, MSCN—National MS Society, USA
  • Pamela Kanellis—MS Society of Canada
  • Julie Kelndorfer—MS Society of Canada
  • Hope Nearhood, MPH, PMP—National MS Society, USA
  • Leslie Ritter—National MS Society, USA


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