The annual flu shot is recommended for everyone to protect against influenza. There are no contraindications based on your thyroid condition or any thyroid drugs you may be taking.
If you have thyroid cancer or are undergoing radioactive iodine (RAI) therapy, which can impair immune function, you are at greater risk of flu complications and need to make every effort to get vaccinated. In the end, the dangers of getting the flu far outweigh any risks, real or presumed.
That is not to suggest there are no risks to getting vaccinated. But most of the adverse effects are either rare or mild, including those associated with autoimmune hypothyroidism or vaccine-induced thyroid symptoms.
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 and autoimmune optic neuritis. While the underlying cause of the activation is not clear, autoimmune diseases like Hashimoto’s and Graves’ are not among the list of concerns.
Risk of Subacute Thyroiditis
There have been several isolated reports—including one from China and another from Turkey—suggesting that subacute thyroiditis (SAT), also called de Quervain thyroiditis or granulomatous thyroiditis, may be triggered by the flu vaccine.
SAT is an inflammatory condition usually triggered by an upper respiratory tract infection that overstimulates the thyroid gland. This is a self-limiting, non-life-threatening disorder that mostly affects middle-aged women and is associated with thyroid pain, difficulty swallowing, hoarseness, fever, fatigue, sweating, and other symptoms.
In both of the aforementioned cases, the vaccine was made with an inactivated (fully killed) virus; the two female patients had no prior history of thyroid disease. Nonsteroidal anti-inflammatory drugs and steroids were used to treat their inflammation and fever. The thyroid drug levothyroxine was used in one patient and increased when her condition relapsed several months later.
While the potential connection is attention-grabbing, 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.
Current CDC Recommendations
The CDC recommends routine yearly flu shot for all people ages six months and older, especially those considered to be at increased risk. These include:
People 50 and olderChildren under fivePregnant womenNursing home and long-term care residentsObese people (those with a BMI of 40 or more)People with suppressed immune systems, including those with cancer or HIVPeople 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.
The only two groups who should not get the flu shot are children younger than six months and people with a known allergy to the flu vaccine or any of its ingredients. This includes people with a severe egg allergy since most flu vaccines are manufactured using egg-based technology.
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 one thing the flu shot cannot do is give you the flu.
A Word From Verywell
Try to make your decision about getting the flu shot without making assumptions about risks which may or may not be relevant or even real. Do your research using reputable sources and speak with your doctor, nurse practitioner, endocrinologist or other healthcare provider to get the facts you need.
If you are afraid of needles, let your healthcare provider 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.
