Do People With Thyroid Disease Need a Flu Shot?

Dispelling Common Myths and Misconceptions

woman getting a shot

Influenza ("the flu") causes widespread illness and death throughout the world, most especially among the elderly, young children, and people with suppressed immune systems. To combat the risk, the Centers for Disease Control and Prevention (CDC) endorses the use of the annual quadrivalent flu vaccine that targets the four highest risk strains predicted for that year.

This includes vaccinations for people with thyroid disorders like Hashimoto's thyroiditis or Graves' disease. While there have been reports that the vaccine may trigger a condition known as subacute thyroiditis, public health officials insist that the benefits of flu vaccination far outweigh the possible risks.

Vaccination Risks

Subacute thyroiditis (SAT), also called de Quervain thyroiditis or granulomatous thyroiditis, is a self-limiting thyroid disorder associated with thyroid pain and other constitutional symptoms. SAT is an inflammatory condition usually triggered by an upper respiratory tract infection which overstimulates the thyroid gland.

Symptoms are typically non-life-threatening and mostly affect middle-aged women. Common signs and symptoms of SAT include:

  • Thyroid gland tenderness
  • Difficulty swallowing
  • Hoarseness
  • Fatigue
  • Fever
  • Frequent bowel movements
  • Hair loss
  • Heat intolerance
  • Irregular or very light menstrual periods
  • Mood changes
  • Nervousness
  • Tremors
  • Heart palpitations
  • Sweating
  • Weight loss, but with increased appetite

Several isolated reports, including one from China and another from Turkey, suggested that SAT may be triggered by the flu vaccine. In both cases, the vaccine was made with an inactivated (fully killed) virus; both women had no prior history of thyroid disease.

Nonsteroidal anti-inflammatory drugs and steroids were used to treat the inflammation and fever. The thyroid drug levothyroxine was used in one of the women and increased when her condition relapsed several months later. Both research teams deemed the SAT events rare and isolated.

While cases like these may suggest that a flu shot can trigger a relapse of thyroid symptoms, particularly in those with hyperthyroidism (overactive thyroid), there is no evidence to date that is possible or even likely.

Autoimmune Disease Risk

Hashimoto's thyroiditis and Graves' disease are two autoimmune disorders in which the immune system targets and attacks the thyroid gland. Hashimoto's is associated with hypothyroidism (low thyroid function) and Graves' is linked to hyperthyroidism.

Given that flu shots work by stimulating the immune system to produce protective antibodies, some people worry that they may also trigger an autoimmune response, essentially "turning on" Hashimoto's or Graves' and causing a symptom relapse.

Most evidence suggests that such an event is unlikely. That is not to say that the vaccine is inherently worry-free. Despite the fact that the flu shot won't instigate an autoimmune thyroid response, several studies have suggested that it may cause a condition broadly described as autoimmune/inflammatory syndrome.

According to the research, the flu vaccine has the potential to activate certain immune-mediated disorders like Guillain-Barré syndrome, autoimmune optic neuritis, multiple sclerosis, and rheumatoid arthritis. While the underlying cause of the activation is not clear, autoimmune diseases like Hashimoto's and Graves' are not among the list of concerns.

Current CDC Recommendations

The CDC recommends routine yearly influenza vaccination for all people ages six months and older, especially those considered to be at increased risk. These include:

  • People 50 and older
  • Children under five
  • Pregnant women
  • Nursing homes and long-term care residents
  • Obese people (those with a BMI of 40 or more)
  • People with suppressed immune systems, including those with cancer or HIV
  • People with certain medical conditions including asthma, COPD, heart disease, diabetes, kidney disorders, and liver disease

The quadrivalent flu shot is made of inactivated (dead) virus as opposed to the FluMist nasal vaccine which contains attenuated (live disabled) virus. Since 2017, the CDC has stopped endorsing FluMist due to administration problems and reduced efficacy rates.

According to the CDC, only two groups should not get the flu shot: children younger than six months and those with a known allergy to the flu vaccine or any ingredient in the vaccine. 

The flu shot is not contraindicated for anyone with a thyroid disease. In fact, those with thyroid cancer or who undergoing radioactive iodine (RAI) therapy are strongly advised to seek vaccination.

Weighing the Pros and Cons

If struggling with whether to get the flu shot or not, it is important to weigh the pros and cons to make a fully informed choice. Among the reasons to get the flu shot:

  • The flu shot can reduce your risk of getting infected.
  • The shot can prevent you from passing the virus to others who may be more vulnerable.
  • You can expect to lose an average of 3½ to 5 workdays if you get the flu.
  • Influenza is a serious disease that has causes between 410,000 and 710,000 hospitalization and between 12,000 and 56,000 deaths in the United States each year.

On the flip side, getting the flu shot doesn't mean that you'll inherently dodge the flu. Sometimes the annual strain will differ from the predicted strain used to formulate the vaccine. What this means is that it's possible to get the flu shot and still get ill. With that being said, you will likely have a less severe bout if you do get vaccinated.

As with all medications, there is a risk of side effects. Most are generally mild and last for only a day or two. Common side effects include:

  • Injection site pain, redness, or swelling
  • Mild fever 
  • Headache
  • Body aches
  • Itching
  • Fatigue
  • Hoarseness
  • Cough
  • Red or itchy eyes

In rare instances, a flu shot may trigger a potentially life-threatening allergic reaction known as anaphylaxis. According to a report the American Academy of Allergy, Asthma, and Immunology (AAAAI), the rate of anaphylaxis following flu vaccination is roughly 1.31 cases per million.

A Word From Verywell

Only you can make the choice as to whether or not you'll get the flu shot; no one can force you. Try to do so without making assumptions about risks which may or may not be relevant or even real. If doubt, speak with your doctor, nurse practitioner, or endocrinologist to get the facts you need.

If you are afraid of needles, let your doctor know so that he or she can walk you through the procedure. Even seeing the size of the needle (a relatively small 22- to 28-gauge) may be enough to assuage your fears.

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