What is the Flu?
The flu is the common name for the influenza virus. It is estimated that every year the virus kills nearly 500,000 people globally. The influenza virus affects the respiratory system and prevents the lungs from effectively performing gas exchange. In other words, the virus prevents the body from taking in air and ensuring that oxygen is exchanged for waste gas like carbon dioxide around the body to supply the cells, tissues, and organs. Influenza mainly causes severe pneumonia followed by a bacterial infection in the lungs. Often the infection is caused by Staphylococcus aureus and Streptococcus pneumoniae. Seasonal epidemics of influenza affect around 5-10% of the population, which burdens the healthcare system. There are four types of influenza: type A, type B, type C, and type D. Type A and type B are the seasonal strains, and the most clinically important for humans.
Influenza A is found in many different animals including humans, birds, and pigs. This virus is divided into subtypes such as H5N1 (Bird flu) or H1N1 (Spanish flu) based on two proteins on the virus’ surface. These proteins are called hemagglutinin (H) and neuraminidase (N). There are 18 subtypes of H while there are 11 subtypes of N. Different combinations of the two proteins create over 130 influenza A subtypes. Some commonly known influenza A subtypes include:
- H1N1: Spanish Flu in 1918 and the Swine Flu in 2009
- H1N2: Endemic virus in pigs
- H2N2: Asian Flu in the 1950s
- H3N2: The 1968 Flu Pandemic
- H5N1: Global Influenza Pandemic in the 2000s
This virus is often only found in humans. Influenza B is divided into two lineages instead of subtypes. There is B/Yamagata influenza and B/Victoria influenza. The incidence of influenza B varies between geographic location and season, but B/Yamagata viruses are less common than B/Victoria globally. While influenza B does not pose as serious of a health risk as influenza A, this virus can cause symptoms such as calf pain, diarrhea, and rhinorrhea.
Influenza C infections are milder than A and B and are not known to cause epidemics. A clinical study characterized the virus as common-cold-like with a fever, cough, and rhinorrhea that persists for typically 2 days.
Influenza D mainly affects cattle and swine but has the potential to spill over into other animals. Very little is known about the virus’ classification and causes.
The flu is highly contagious and can spread easily from person to person through coughing, sneezing, or touching contaminated surfaces.
Symptoms of the Flu
Influenza flu symptoms include
- Myalgia (muscle pain)
- Sore throat
- Dry Cough
- Nasal Congestion
In some cases, the flu can lead to more severe complications such as pneumonia, bronchitis, pericarditis, and myocarditis. For pregnant individuals, there is an increased risk of prematurity, lower birth weight, maternal complications, and infant perinatal mortality if left untreated.
What is the Flu Shot?
The flu shot is a vaccine that is designed to protect against H1N1, H3N2, and B strains of the seasonal influenza virus. The vaccine contains inactivated or weakened viruses that will then induce the body’s immune system to produce antibodies and learn to recognize the virus. By teaching the body’s antibodies what the virus looks like, they can help protect against future infections. Did you know that some traditional influenza vaccines that use inactivated viruses are prepared using chicken eggs? Whole viruses are inoculated in chicken eggs before they are harvested and chemically inactivated using formalin. In other words, the chicken eggs act as an incubator to allow the virus to replicate. There are two main purposes for the vaccine: one, to protect the vaccinated individual from infection and disease, and two, to promote herd immunity, where a large portion of the population is immune to the disease which limits its spread.
The flu is highly contagious and can cause severe health complications, hospitalization, and for some, death. Getting a flu shot is crucial for preventing the spread of the virus and protecting both yourself and the community. Today’s vaccines are estimated to be 40 to 60% effective, but effectiveness can vary on factors such as age, the vaccinees’ pre-existing health conditions, and their level of exposure. The seasonal strain of the virus may also differ from what is in the vaccine, as influenza is a virus that is capable of mutating very easily. New strains will be stronger than previous strains, but getting the vaccine can help lessen the severity of the symptoms if you do still catch the flu.
The flu shot is recommended for anyone over six months old. Children are recommended to get two doses of the vaccine 4 weeks apart if they are between 6 and 59 months old. Always consult with your healthcare professional to get an educated timeline of when you should get vaccinated.
Who is at High Risk of the Flu?
- Unvaccinated infants between 12 to 24 months old
- Individuals with cancer and/or are receiving chemotherapy or radiotherapy
- Individuals with sickle-cell anemia
- Individuals with asthma or other chronic pulmonary diseases
- Individuals with immunosuppressive disorders
- Individuals with chronic renal dysfunction (kidney disease)
- Individuals with chronic metabolic diseases like diabetes
- Individuals over the age of 65
It is important to prevent the spread of the flu by practicing good hygiene such as washing your hands frequently and covering your mouth when coughing or sneezing. During flu season, it is encouraged that you get your flu vaccination.
Should I get the flu shot if I have a thyroid condition?
Many people with thyroid conditions are most worried about the vaccine causing an autoimmune response. Autoimmune thyroid diseases such as Graves’ Disease, and Hashimoto’s Thyroiditis are two major autoimmune conditions that cause hyperthyroidism and hypothyroidism, respectively. The flu shot is meant to stimulate the immune system and release antibodies to teach the body how to respond to a future infection. There is little epidemiological evidence to suggest the flu shot can induce an autoimmune flare-up. Many studies argue that the benefits of getting vaccinated outweigh any potential risks.
If you are worried, you need to discuss your concerns about getting the vaccine for a thyroid condition with your healthcare professional and make an informed decision about whether or not to get vaccinated.
According to the Centers for Disease Control and Prevention (CDC), only the following people SHOULD NOT get the vaccine:
- Children younger than 6 months old
- Individuals with severe allergies to ingredients in the vaccine such as gelatin or antibiotics.
- Individuals who have had an allergic reaction to an influenza vaccine in the past.
Why Should You Get Vaccinated if You Have Thyroid Cancer?
If you have thyroid cancer, getting the vaccine is highly recommended. In cancer patients, the immune system is suppressed by treatments, therapies, and even cancer itself. This leaves them at higher risk of infections such as influenza A and B. By getting vaccinated, the duration and severity of infection can be reduced and prevent further health complications.
One study found no association between getting the influenza vaccine and an increase in immune-related adverse events. It concluded that cancer patients should receive the influenza vaccine, but to have a medical professional’s opinion as other factors such as genetics and medications can impact the vaccine’s effectiveness.
Is there a Risk of Subacute Thyroiditis?
Subacute thyroiditis is an inflammatory condition that occurs in nearly 5% of patients with a thyroid disease. The condition is difficult to diagnose as the causes are fairly unknown, but it is often characterized by thyroid gland swelling, fever, fatigue, sweating, and thyrotoxicosis. There have been some cases of patients developing subacute thyroiditis after receiving the influenza vaccination. A 40-year-old woman in Japan presented with a swollen thyroid gland and was diagnosed with subacute thyroiditis after receiving the influenza vaccine and a second dose of the Moderna COVID-19 vaccine. The patient recovered, however, the cause was unclear. The study concluded that it is necessary to obtain a vaccination history before diagnosing a patient with subacute thyroiditis.
Another 36-year-old female patient in Australia reported developing subacute thyroiditis 30 days after receiving the H1N1 vaccine. She had no prior history of thyroid disease. After being treated with propranolol over several weeks, there was a gradual improvement in her condition.
While there is a potential connection between subacute thyroiditis and the influenza vaccine, it is extremely rare as only nine cases have been documented globally. There is no solid evidence to suggest that vaccination is the sole cause of the inflammatory condition.
- Influenza is estimated to kill nearly 500,000 people globally.
- There are four types of influenza: type A, type B, type C, and type D. Type A and type B are the seasonal strains, and the most clinically important for humans.
- The flu is highly contagious, so getting a flu shot is crucial for preventing the spread of the virus and protecting both yourself and the community.
- Influenza flu symptoms include fever, myalgia (muscle pain), headaches, sore throat, dry cough, nasal congestion, nausea, vomiting, diarrhea, and fatigue.
- You CAN get vaccinated if you have a thyroid condition. There is little evidence that suggests otherwise.