People living with multiple sclerosis (MS) again face the choice of whether to get an updated messenger RNA (mRNA) COVID-19 vaccine. Scientific research has consistently shown that vaccinations are instrumental in protecting people from severe cases of COVID-19 — and that goes for people with MS. Still, some people with MS worry that getting the vaccine may trigger a multiple sclerosis relapse — that is, that it may trigger symptoms in people whose MS is under control.

Based on the most current research, a small percentage of people with MS have experienced acute (brief) relapses following a COVID-19 vaccination — and at about the same rate that unvaccinated people with MS have developed relapses. Relapses following vaccinations have generally been treatable. Importantly, researchers have found that a COVID-19 infection itself can also trigger MS relapses.

Overall, credible health experts from agencies agree that the benefits of a COVID-19 vaccine for people with MS outweigh any potential risk — especially considering that people with MS are at a higher risk of severe COVID-19, which can result in hospitalization or death.

“As of September 12, 2023, individuals ages 6 months and older should receive an updated vaccine dose,” according to the National Multiple Sclerosis Society. “Stay up to date with COVID-19 vaccines through the CDC schedules, and talk to your MS health care provider to determine what is best for you.” (“CDC” refers to the U.S. Centers for Disease Control and Prevention.)

Read on to learn about the new mRNA COVID-19 vaccines as well as what the latest research says about COVID-19 vaccines — and other types — for people with MS. Equipped with this knowledge, you and your health care team can have an informed conversation about when and if a COVID-19 vaccination is right for you.

The New Monovalent COVID-19 Vaccines

The U.S. Food and Drug Administration (FDA) has approved a new round of updated mRNA COVID-19 vaccines for adults and children ages 6 months and up. These new versions of the Moderna and Pfizer vaccines are recommended by the CDC.

In the previous round, mRNA vaccines were bivalent, meaning they contained blueprints of spike proteins found in two different versions of SARS-CoV-2, the virus that causes COVID-19. These new vaccines are monovalent — they contain the blueprints of a single variant, called Omicron variant XBB.1.5 and nicknamed “Kraken.”

Health experts have identified XBB.1.5 as being highly transmissible and contagious. People who’ve received previous vaccinations or previously had COVID-19 have still been infected with this newer variant.

Who Should Get the New Vaccine?

All people ages 5 and up are eligible for one dose of the new vaccine as long as it’s been at least two months since their last vaccination. Children 6 months to 4 years old may receive more than one dose of the new vaccine, depending on their vaccination status.

People who are moderately or severely immunocompromised (have weakened immune systems) also should receive the new vaccine. The CDC cautions that these people are “at increased risk of severe COVID-19 illness and death.”

Are the New Vaccines Safe?

The FDA based its approval of the new mRNA vaccines on the safety and effectiveness of previous versions, which were manufactured in the same way as the new round. Per the CDC, millions of Americans have received COVID-19 vaccines “under the most intense safety monitoring program in U.S. history.”

The FDA noted that the benefits of receiving the vaccine outweigh any risks. Potential side effects — both common and rare but serious — are similar to those of previous versions of the vaccine. Common side effects are generally similar to flu symptoms, including temporary fever, chills, aches, and fatigue, along with irritation or soreness at the injection site.

COVID-19 Vaccinations and MS Relapses: What Are the Risks?

Several research studies have investigated the effects of COVID-19 vaccines on people living with MS. One from 2021 found that among 388 people with relapsing-remitting MS (RRMS) who received the Pfizer BNT162b2 mRNA vaccination, eight (2.1 percent) experienced acute MS relapses within 10 to 19 days of their first dose. Of the 306 of those with RRMS who received a second dose, five (1.6 percent) experienced acute relapses within 14 to 21 days.

Notably, researchers found this relapse rate was similar among people with RRMS who hadn’t received a vaccination.

A second study, published in the Journal of Clinical Neuroscience in 2022, went into more detail as to what sort of acute MS relapses people experienced after receiving COVID-19 vaccinations. It looked at 29 specific case studies of people from around the world who developed MS relapses after receiving any type of COVID-19 vaccine (not just mRNA vaccines) from Pfizer and Moderna.

On average, the individuals experienced MS relapses within around 8 days of receiving their vaccinations. The most common MS-related symptoms, experienced by 14 people, were sensory deficits, including:

• Paresthesia — Unusual sensory symptoms, like pins and needles, crawling bugs, or tickling
• Dysesthesia — Unusual and spontaneous pain sensations, like burning, an electric shock, or shooting pain
• Hypoesthesia — Reduction in any sensitivity to any sensation, such as temperature
• Numbness

Additionally, six of the participants experienced weakness.

Most of the participants received glucocorticoids as treatment for their relapse. In terms of recovery:

• Thirteen recovered fully.
• Five recovered partially.
• Five had not recovered by the end of the study.

Researchers from the 2021 study published in the journal Multiple Sclerosis also found that 2 percent of all participants — which included people with various types of MS — briefly experienced worse MS symptoms after their first dose. After receiving a second dose, 4.8 percent had worse MS symptoms. These worsened symptoms lasted one to two days and were mainly associated with flu-like symptoms. A few participants experienced tingling in their faces, but it passed quickly.

Other Common Side Effects

Overall, researchers found that, following the first vaccination, 29.7 percent of participants developed at least one kind of adverse event (i.e., a side effect, including an acute MS relapse). Among those who received a second dose, 40.2 percent had an adverse event.

The most common side effects included:

• Pain at the injection site
• Fatigue
• Headaches
• Muscle or joint pain
• Flu-like symptoms (fever, chills or a combination of both)

Aside from pain at the injection site, all of these side effects were more prevalent after people received their second dose. All of these side effects went away on their own within a few days.

The 2021 study author’s conclusion was that mRNA vaccines are safe for people with MS and did not increase their risk of relapse.

The 2022 study authors reached a similar conclusion: “Overall, the COVID-19 vaccination may trigger relapses in some MS patients but as the infection itself can stimulate relapse, the benefit of vaccination outweighs its risk in this population, and mass vaccination against COVID-19, especially in MS patients should be continued and encouraged,” they wrote. “In the meanwhile, most of the relapsed cases were fully recovered after receiving methylprednisolone showing the relapse can be controlled without consequences.”

Other COVID-19 Vaccination Consideration for People With MS

According to the Multiple Sclerosis Society, the following groups are at the highest risk of hospitalization from COVID-19 and are especially encouraged to get vaccinated:

• Those with progressive MS
• Older individuals
• People with higher levels of physical disability
• Those with other medical conditions, such as diabetes, hypertension (high blood pressure), and heart and lung disease

Additionally, according to the Multiple Sclerosis Society, COVID-19 vaccinations are safe to use alongside MS medications. Some disease-modifying therapies (DMTs) can render the vaccine less effective because they suppress your immune system, but they still offer some protection. The nonprofit recommends that people coordinate the timing of their vaccination if they’re taking any of the following:

• Alemtuzumab (Lemtrada)
• Ocrelizumab (Ocrevus)
• Ofatumumab (Kesimpta)
• Rituximab (Rituxan)
• Ublituximab (sold as Briumvi)

In addition to getting vaccinated, people with MS should consider taking the following precautions to protect themselves — particularly those who are taking a DMT or are in a high-risk group:

• Wear a high-quality mask or respirator, and make sure it fits properly.
• Steer clear of crowded spaces with limited ventilation.
• Wash your hands frequently with soap and water and/or use hand sanitizer containing at least 60 percent alcohol.
• Learn about the symptoms of COVID-19 and monitor your health for any of them.
• Take necessary precautions if you’ve been exposed to COVID-19.
• Use FDA-approved COVID-19 tests as directed.
• Know how to get in touch with your doctor quickly, including during their off-hours.

If you do contract COVID-19, contact your health care provider immediately — the sooner you begin treatment such as an oral antiviral treatment, the better your outcome is likely to be. Additionally, to protect your health and to keep others safe, the CDC recommends that you isolate for at least 10 days.

Find Your Team

On MyMSTeam, the social network for people with multiple sclerosis and their loved ones, more than 203,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

What are your plans for the updated COVID-19 vaccine? What questions, concerns, or advice do you have? Share your experience in the comments below, or start a conversation by posting to your Activities page.