What is multiple sclerosis?

In multiple sclerosis (MS), the immune system attacks the brain and spinal cord. This damages nerves and the tissue that covers and protects nerve fibers. Damage to this protective tissue changes how the nerves deliver signals from the brain and spinal cord. The nerve damage can produce many different symptoms, including fatigue, numbness, weakness, vision change, and loss of balance. The course of the disease is unpredictable, and severity often varies between individuals.

Can getting a flu shot or other vaccination cause MS?

Getting certain vaccines is not likely to increase the risk of developing MS. There is some evidence from the research that shows there is no identified link between certain vaccines and MS. However, for other vaccines, including the flu shot, there is a lack of consistency in the research to exclude a link completely. However, there are known risks that getting sick with the flu can cause an MS relapse.

I have MS. Should I get vaccines?

For people with MS, preventing infections through vaccine use is a key part of medical care. If you have MS, you should receive vaccines according to the standard vaccine guidelines. You should receive the flu shot every year unless your doctor has advised you not to for a specific reason. For example, if you have had an allergic reaction to the flu shot before, you may want to avoid getting it now. Experiencing an MS flare is another reason to at least delay receiving a flu shot (see below).

If you are using a disease-modifying drug for MS, talk with your doctor about which shots are safe for you. Depending on the disease-modifying drug you take, you may need to avoid some shots. For instance, there is some evidence that vaccinations for flu and tetanus may not protect against these infections when you are taking certain disease-modifying drugs, even when you are not experiencing a flare.

In addition, the live forms of vaccines (those using a weakened version of the disease-causing germ) generally should be avoided by people with MS who are taking disease-modifying drugs, especially steroids used to treat active MS flares. The exception is when infection risk is high and killed forms of these vaccines (those using an inactive version of the disease-causing germ) are not available.

Currently, research exploring a link between live vaccine use and infection risk is lacking. But experts think that using a live vaccine when you have a suppressed immune system may be risky. Also, for several disease-modifying drugs for MS, the prescribing information recommends avoiding the use of live vaccines.

Can getting a flu shot or other vaccine make my MS symptoms worse?

According to the guideline, the available studies were not designed well enough to tell whether vaccines can cause MS flares or make them worse. Future studies that give more reliable information may help to answer this question.

At the same time, there is a risk of MS relapse from flu infection. In addition, flu infection can lead to serious illness and death for people with severe chronic disease.

I am having an MS flare. Can I still get my flu shot?

The guideline recommends waiting until long after a flare has passed before getting any vaccine shots. Often, the waiting period can last many weeks after the relapse has started. Even though the evidence is limited, experts remain concerned that vaccinations may make relapses worse.

If you are having an MS flare, talk with your doctor or care team about the best approach for you. Most vaccinations are not emergencies, so waiting until the flare has passed before getting any vaccinations is often the best approach.

Do MS disease-modifying drugs make immunizations less effective?

Despite the limits of the evidence regarding vaccinations and MS flares, some experts suspect that some medicines used to treat MS—such as fingolimod, glatiramer acetate, mitoxantrone—may make vaccines less effective. In addition, steroids for treating active MS flares may make vaccines from live viruses less effective.

Read the full practice guideline summary.

Read the full summary of the guideline for patients and their families.