The flu is a contagious respiratory sickness that generally causes fever, aches, chills, headaches, and in some cases, more serious issues. It’s an especially big concern if you’re living with multiple sclerosis (MS).

Scientists have linked the flu to MS relapse. That’s why getting the flu vaccine is so important. At the same time, it’s important for people living with MS to get a flu shot that won’t interfere with their current treatment plan.

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

The majority of people with MS come down with an average of two upper respiratory infections per year, according to a 2015 review in Frontiers in Immunology. Scientists found that these types of illnesses, such as colds and flu, doubled the risk of a person living with MS experiencing a relapse.

The review also noted that after people with MS got an upper respiratory infection, an estimated 27 to 41 percent experienced a relapse within 5 weeks. Scientists have also found that the likelihood of relapse is seasonal, typically peaking in the spring.

In addition, some medications that you may be taking for MS can affect your immune system and put you at higher risk for serious complications from the flu.

Although more studies are needed, research in animals suggests that respiratory infections may encourage the movement of immune cells into the central nervous system. In turn, this may trigger an MS relapse.

In a 2017 study published in PNAS, scientists injected mice that were genetically prone to autoimmune disease with the influenza A virus. They found that about 29 percent of the mice that received the virus developed clinical signs of relapse within two weeks of the infection.

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

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.

However, before receiving the vaccine, it’s important to talk to your healthcare provider. The timing and type of MS medication you’re taking, along with your general health, may affect your flu vaccine options.

In general, the AAN recommends against people with MS taking live vaccines, such as the flu vaccine nasal spray. This is especially important for people who use certain disease-modifying therapies (DMTs) to treat MS.

If you’re experiencing a serious relapse, your doctor will likely recommend that you wait 4 to 6 weeks after the onset of the symptoms to get vaccinated.

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

According to the Rocky Mountain MS Center, flu vaccines are about 70 to 90 percent effective, but that efficacy could be lower in people with MS taking medications that affect their immune systems.

In general, the AAN recommends people with MS get a non-live form of the flu vaccine. Vaccines come in different forms:

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

The flu shots currently available are non-live forms of vaccine, and 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, recently used, or plan to use certain disease-modifying therapies (DMTs) for MS.

The National MS Society notes which DMTs, and the timing of treatment, may cause concern if you’re considering a live vaccine.

It’s considered safe to get an inactivated flu vaccine even if you’re taking one of these medications:

  • interferon beta-1a (Avonex)
  • interferon beta 1-b (Betaseron)
  • interferon beta 1-b (Extavia)
  • peginterferon beta 1-a (Plegridy)
  • interferon beta 1-a (Rebif)
  • teriflunomide (Aubagio)
  • glatiramer acetate (Copaxone)
  • fingolimod (Gilenya)
  • glatiramer acetate injection (Glatopa)
  • alemtuzumab (Lemtrada)
  • mitoxantrone hydrochloride (Novantrone)
  • dimethyl fumarate (Tecfidera)
  • natalizumab (Tysabri)
  • ocrelizumab (Ocrevus)

For adults ages 65 and older, Fluzone High-Dose is available. It is an inactivated vaccine, but researchers have not studied how it works in people with MS. Talk to your doctor if you’re considering this vaccine option.

In addition to getting vaccinated, you can do plenty of things to reduce your risk of getting colds and the flu. The Centers for Disease Control and Prevention (CDC) recommends that you:

  • Avoid contact with people who are sick.
  • Stay home if you’re ill.
  • Wash your hands regularly with soap and water or an alcohol-based cleanser.
  • Cover your nose and mouth when you sneeze.
  • Disinfect commonly used surfaces.
  • Get plenty of sleep and eat a healthy diet.

If you’re living with 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 living with MS, and it increases the risk of relapse. If you’re experiencing symptoms of the flu, visit your healthcare provider as soon as possible.