Key takeaways:
The flu causes thousands of deaths each year. The flu shot is the most effective way to prevent serious flu complications.
You cannot get the flu from the flu shot. Serious side effects, like severe allergic reactions or Guillain-Barré syndrome, are extremely rare.
The flu shot is safe for most people over 6 months old, including children, pregnant women, and people with chronic medical conditions.
Influenza (or the flu) is a common respiratory illness caused by influenza viruses. It can make you feel pretty sick. It can also cause serious illness, hospitalization, and even death. In the U.S., roughly 5,000 to 50,000 people die every year from the flu. The flu shot is the best protection against the the flu virus.
The flu shot has been around for decades, and there’s plenty of research to support how safe and effective it is. But it’s understandable to have questions and concerns. Let’s take a closer look at the research so you can make the best choice.
Can you get sick from the flu shot?
You cannot get the flu from a flu vaccine.
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Some people feel a bit under the weather after getting the flu shot. This doesn't mean you got sick with the flu. This is actually a sign that your body is responding to the vaccine. When you get a vaccine, your immune system works faster than normal to create antibodies that will protect you if you get exposed to the flu later on. This can make you feel mildly ill, but this feeling usually goes away within a few days.
Is the flu shot safe?
Yes, the flu shot is safe.
There are a lot of misconceptions about the safety of the flu shot. Many organizations monitor vaccine safety, like the World Health Organization (WHO), the CDC and the FDA. The CDC has three systems to monitor vaccine safety:
Vaccine Adverse Event Reporting System (VAERS) is a national program that tracks side effects or other problems with vaccines.
Vaccine Safety Datalink (VSD) is a joint program between the CDC and nine other healthcare organizations to track the safety of vaccines.
Clinical Immunization Safety Assessment (CISA) Project evaluates vaccine safety and does high-quality research with major medical centers.
Over the past 10 years, more than 1 billion flu shots have been given in the U.S. Safety monitoring data show that the risk of a serious side effect is about 1 in 1 million.
What side effects can flu vaccines cause?
All medical treatments can cause side effects, including the flu vaccine. There are three main side effects you should know about
Nonallergic reactions to the flu shot
Most people who experience side effects after a flu shot only have mild symptoms, like injection site reactions or flu-like symptoms. These symptoms usually go away in 1 to 2 days and can include:
Arm soreness (most common)
Itching
Fatigue
Cough
Low fever
Body aches
Headaches
Mild reactions are a normal response to vaccines. They are signs that your immune system is responding to the vaccine.
Some people can also experience a brief fainting spell after getting a flu shot. This is especially common in teens. And in very rare cases, people can experience ongoing pain or stiffness at the injection site.
Allergic reactions to the flu shot
You can have an allergic reaction to the flu vaccine. This is usually caused by an allergic reaction to other vaccine components, not the influenza virus fragments.
Allergic reactions to the flu shot can range from mild to severe. Mild reactions are not life-threatening. They can include symptoms like:
Hives
Runny nose or cough
Vomiting or diarrhea
A severe reaction — anaphylaxis — is serious and can be life-threatening. Symptoms of anaphylaxis include:
Swelling of the face, lips, tongue, or throat
Trouble breathing
Dangerously low blood pressure
These reactions are rare. The chance of having an allergic reaction is about 1 in 1 million.
Guillain-Barré syndrome
The flu vaccine has also been linked to Guillain-Barré syndrome (GBS). GBS is a serious autoimmune condition that causes temporary paralysis. It usually starts in the legs and can slowly work its way up the body. Even though these symptoms get better, this medical emergency can be scary.
The risk of getting GBS from the flu shot is extremely small — about 1 in 1 million. Meanwhile, the flu virus causes GBS in 17 out of 1 million people. That means you’re about 17 times more likely to develop GBS after a flu infection than after a flu shot.
Can you get a flu shot while you're sick?
You should let your healthcare team know if you feel sick and you're scheduled to get a flu shot. Most experts agree that it’s safe to get the flu shot if you have a minor illness, like a cold or upper respiratory tract infection. But you may need to hold off on getting the flu shot if you have a more serious illness.
Is the flu shot safe for babies and children?
Yes, the flu shot is also safe for children and babies over 6 months. The flu shot does not cause the flu in children. There is no clear evidence that the flu shot causes autism.
The flu can cause serious illness in children. A yearly flu shot can protect children from serious flu-related illness.
Is the flu shot safe for pregnant women?
The flu shot is safe for pregnant women.
Experts recommend that pregnant women get vaccinated against the flu because they are at higher risk for severe flu illness. You're more likely to be hospitalized or die from the flu if you are pregnant. The flu can also increase the risk of complications like:
Miscarriage
Preterm labor
Premature birth
Is the flu shot safe for people with chronic medical conditions?
Yes. In fact, it’s especially important for people with chronic medical conditions to have a flu shot. The flu can also be especially dangerous for:
Adults 65 years old and up
People have a weakened immune system including people with cancer
People living in nursing homes and other long-term care facilities
People with diabetes
People with heart failure
People with lung conditions, like chronic obstructive pulmonary disease (COPD), and asthma.
Should you get a flu shot?
Every choice has pros and cons, including getting the flu vaccine. But, for most people, the flu shot is likely to do more good than harm. The risks of a serious reaction to a flu vaccine is very low. Compared with the flu shot, having the flu is actually pretty risky.
The flu shot can keep you from getting sick, and it even protects you if you do still end up getting the flu.
But some people should not get the flu shot. This includes people who have:
A moderate or severe illness. These people should wait until they feel better to get their flu shot.
A history of Guillain-Barré syndrome
A history of anaphylaxis after receiving the flu vaccine
Talk with your healthcare team if you’re unsure whether the flu shot is right for you. They understand your health history. Together, you can review the benefits and risks of getting a flu shot and so you can make the best decision for your health.
Frequently asked questions
It’s common to feel a little unwell after getting a flu shot. You might feel some soreness around where you got the shot, or you might feel some body aches or tiredness. These symptoms just mean that the flu shot is working by causing your immune system to ramp up and make antibodies that will protect you from the flu.
Most people only experience side effects for a day or two after getting a flu shot. Some people only experience symptoms for a few hours.
You can manage your mild side effects from the flu shot by taking over-the-counter (OTC) medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). This can help treat any fever or achiness you may have.
It’s possible to experience delayed reactions to the flu vaccine. But this is rare. The most common delayed reactions are enlarged lymph nodes or a rash. These symptoms usually show up within a few hours or days of getting the flu shot. But it’s possible for them to show up 2 to 3 weeks later.
The flu shot doesn’t cause dementia. In fact, new research suggests that regular flu shots may protect you against developing Alzheimer’s disease. In a 2020 study, having at least one flu shot decreased cases of Alzheimer’s by 17%. Repeat flu shots decreased it by another 13%.
It’s common to feel a little unwell after getting a flu shot. You might feel some soreness around where you got the shot, or you might feel some body aches or tiredness. These symptoms just mean that the flu shot is working by causing your immune system to ramp up and make antibodies that will protect you from the flu.
Most people only experience side effects for a day or two after getting a flu shot. Some people only experience symptoms for a few hours.
You can manage your mild side effects from the flu shot by taking over-the-counter (OTC) medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). This can help treat any fever or achiness you may have.
It’s possible to experience delayed reactions to the flu vaccine. But this is rare. The most common delayed reactions are enlarged lymph nodes or a rash. These symptoms usually show up within a few hours or days of getting the flu shot. But it’s possible for them to show up 2 to 3 weeks later.
The flu shot doesn’t cause dementia. In fact, new research suggests that regular flu shots may protect you against developing Alzheimer’s disease. In a 2020 study, having at least one flu shot decreased cases of Alzheimer’s by 17%. Repeat flu shots decreased it by another 13%.
The bottom line
The flu isn’t just a bad cold — it can lead to serious complications, especially for young children, older adults, and people with certain health conditions. The flu shot cannot give you the flu, and severe side effects are extremely rare. For most people, the risk of getting seriously sick from the flu is much higher than the risk of problems from the vaccine. Talk with your healthcare team if you're unsure if the flu shot is right for you. They can help you weigh the benefits and risks based on your personal health history.
Why trust our experts?
References
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Centers for Disease Control and Prevention. (2023). Flu vaccine safety.
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Centers for Disease Control and Prevention. (2024). About the Vaccine Adverse Event Reporting System (VAERS).
Centers for Disease Control and Prevention. (2024). About the Vaccine Safety Datalink (VSD).
Centers for Disease Control and Prevention. (2024). Fainting and vaccines.
Centers for Disease Control and Prevention. (2024). Guillain-Barré syndrome (GBS) and vaccines.
Centers for Disease Control and Prevention. (2024). How vaccine safety monitoring works.
Centers for Disease Control and Prevention. (2024). Seasonal flu vaccines.
Centers for Disease Control and Prevention. (2024). Who needs a flu vaccine.
Children’s Hospital of Philadelphia. (2021). Vaccines and Guillain-Barré syndrome.
Chow, E. J., et al. (2019). Influenza virus-related critical illness: Prevention, diagnosis, treatment. Critical Care.
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National Foundation for Infectious Diseases. (2015). Can a flu vaccine give you the flu?
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