Getting the flu may increase your risk of relapse with multiple sclerosis (MS). Some preventive steps, such as getting vaccinated and avoiding crowds during flu season, may help.

The flu can be especially dangerous when you live with multiple sclerosis (MS).

Infections, including the flu, may potentially increase the risk of MS relapse. But it’s important to get a flu shot that won’t interfere with your current treatment plan.

Read on to learn how the flu may cause relapse in people with MS and how to protect yourself.

People with chronic conditions generally have a greater risk of getting the flu and of experiencing severe illness and other complications if they become sick.

Additionally, some medications for MS can suppress your immune system, putting you at higher risk for infection and serious complications from the flu.

A compromised immune system can be less effective at responding to infections, increasing the likelihood that you’ll get sick and have a more severe course of illness.

Upper respiratory infections, including the flu and SARS-CoV-2, may increase the risk of MS relapses and pseudoexasperations. But more studies are still needed in this area.

Research in animals suggests that respiratory infections may encourage the movement of immune cells into the central nervous system, which in turn may trigger an MS relapse.

In a 2017 study, scientists injected the influenza A virus into mice that were genetically prone to autoimmune disease. They found that about 29% of the mice that received the virus developed clinical signs of relapse within 2 weeks of the infection.

The researchers also monitored immune cell activity in the mice, noting increased activity in the central nervous system. They suggest that the viral infection triggered this change, which may be the underlying reason that infections worsen MS.

However, a 2023 study involving human participants with MS didn’t find a strong link between infection and MS relapse in people who were treated with disease-modifying therapies (DMTs).

A 2022 research article notes that upper respiratory and bladder infections may cause pseudo-relapses, or periods of time when a person has symptoms similar to those of a previous relapse but without new inflammatory activity.

The American Academy of Neurology (AAN) considers vaccinations an essential part of medical care for people living with MS. The AAN recommends that people with MS get the flu vaccine every year.

The timing and type of MS medication you’re taking, along with your overall health, may affect your flu vaccine options, so it’s important to talk with a healthcare professional before getting a vaccine.

The AAN does not recommend that people with MS get live vaccines such as the flu vaccine nasal spray. This is especially important for people who use certain DMTs to treat MS.

If you experience a serious relapse, the guidelines recommend that you wait until the relapse is no longer active to get vaccinated. This may be many weeks after you develop symptoms.

If you’re considering switching treatments or starting a new treatment, the guidelines recommend that you get vaccinated 4 to 6 weeks before starting a treatment that will suppress or modulate your immune system.

A vaccine may be less effective in people with MS who take medications that affect their immune systems.

The AAN recommends that people with MS get a non-live form of the flu vaccine. Vaccines come in two forms:

  • Non-live: These vaccines include an inactivated, or dead, virus or only proteins from the virus.
  • Live: Live-attenuated vaccines contain a weakened form of the virus.

The flu shots currently available are non-live forms of vaccine, and they are generally considered safe for people with MS.

The flu nasal spray is a live vaccine, and it isn’t recommended for people with MS. It’s especially important to avoid live vaccines if you use, have recently used, or plan to use certain DMTs for MS.

In addition to getting vaccinated, you can take steps to reduce your risk of getting the flu. These preventive measures may also reduce your risk of contracting other viral infections. The Centers for Disease Control and Prevention (CDC) recommends:

  • avoiding contact with people who are sick
  • staying home if you’re sick
  • washing your hands regularly with soap and water or an alcohol-based cleanser
  • covering your nose and mouth when you sneeze
  • disinfecting commonly touched surfaces such as doorknobs
  • improving air quality indoors to reduce virus particles in the air or meeting people outdoors, where there are fewer virus particles

If you have MS and think you may have the flu, it’s best to contact a healthcare professional. They can order a diagnostic test and determine whether you need treatment.

The CDC recommends that people who are at risk of severe complications of the flu receive treatment.

Doctors can treat the flu with antiviral medications. These drugs work best if you start taking them within 1 to 2 days of the start of your symptoms, but they may still have some benefit if started later. In addition to taking medication as prescribed for the full course of treatment, doctors may recommend:

  • drinking extra fluids such as water, broth, and herbal tea
  • eating nutritious meals
  • getting extra rest
  • taking preventive measures to protect those around you from illness

Do MS symptoms get worse when sick?

Your MS symptoms may return or worsen when you are sick. If there is no new inflammatory activity, this is known as a pseudo-relapse. Illness may also trigger a relapse or exacerbation.

Is the flu worse when you have MS?

If you get the flu while you have MS, you may be at a greater risk of severe illness or complications. This risk may be higher if you’re taking medications that affect your immune system.

Does MS make you more susceptible to illness?

Having MS may increase your risk of illness, particularly if you’re taking DMTs that suppress your immune system. This makes it harder for your body to effectively respond to an infection.

If you have MS, it’s especially important to get the flu vaccine every year. Discuss the medications you’re taking with your doctor and decide on a plan for the timing of your flu vaccine.

The flu can be more serious in people with MS and may increase the risk of relapse. If you’re experiencing symptoms of the flu, talk with a healthcare professional as soon as possible to find out whether they recommend treatment.