Key takeaways

  • The flu shot will not give a person influenza, or the flu. Instead, it should help prevent the infection, which causes a significant number of visits to the doctor in the United States each year.
  • The flu vaccine can cause some mild side effects, such as a fever, headache, or soreness at the injection site. These are temporary and usually less severe than flu symptoms.
  • Flu complications can be serious, regardless of a person’s age and health status. People can speak with their doctor for more information about the benefits and risks of flu vaccines.

The belief that flu vaccines can cause the flu is a major reason for vaccine hesitancy in the United States. However, this belief is a misconception.

In this article, learn about why the flu shot does not cause the flu, some reasons a person might get sick after getting a vaccine, and how the shot helps protect against illness.

Some people believe that the flu vaccine contains living viruses and can give a person the flu. This is not true.

Scientists make the most common flu vaccine using an egg-based manufacturing process. The vaccine contains inactivated, or dead, flu viruses.

When a health professional injects the vaccine into a person’s body, the person’s immune system starts to develop antibodies to fight the illness — even though the virus is inactive.

If a person comes into contact with flu virus again, their body will recognize it and already has the right antibodies to attack it quickly and keep a person from getting sick.

Flu vs. vaccine side effects

Many other misconceptions about the flu shot causing the flu are due to the side effects a person can experience after they get the shot.

Examples of these side effects include:

According to the Centers for Disease Control and Prevention (CDC), these symptoms tend to appear shortly after receiving the shot and will go away within 1 to 2 days.

Usually, flu vaccination side effects are less severe than symptoms of the flu.

Flu resources

For more information and resources to help keep you and your loved ones healthy this flu season, visit our dedicated hub.

There are several reasons a person may get sick after receiving a flu shot.

Some people may think that they have the flu when they are ill due to a different viral or bacterial infection. This is because many flu symptoms are similar to those of the common cold, which can also occur during flu season.

It takes about 2 weeks for a person to develop immunity to the flu after receiving a flu shot. During this time, it is possible that a person could be exposed to the flu virus and become sick.

The flu vaccine represents researchers’ best predictions about which flu virus strains will be most prevalent for that year. However, a person can still come into contact with a strain of flu virus that they are not immunized against.

The primary benefit of getting the flu shot is preventing the illness. This also helps prevent its symptoms, including high fevers, chills, a racking cough, muscle aches, and extreme fatigue.

Getting the flu shot also contributes to something called “herd immunity.” Herd immunity helps prevent the overall incidence of flu, as people who get the vaccine do not get the flu and therefore cannot pass it to other people.

The CDC estimates that for the 2024 to 2025 flu season, the flu shot prevented:

  • around 10 million flu-related illnesses
  • around 5 million flu-related medical visits
  • 180,000 flu-related hospitalizations
  • 12,000 flu-related deaths

The flu can be life threatening to people of all ages. Even young people without preexisting health conditions can die from flu complications. It is important not to underestimate the seriousness of this illness.

Anyone can experience flu complications. However, some people are more likely than others to experience the most severe side effects of the flu.

People at risk of complications include:

Even if a person does not fall into any of these categories, getting the flu vaccine helps protect those at greater risk.

Getting the flu shot will not give a person the flu. It can protect against getting the virus and spreading it to others.

Although a person may have some mild feelings of discomfort for a few days after getting a flu shot, they are usually minor symptoms. Getting the flu itself can cause symptoms that are much more severe.

Doctors usually release the flu vaccine in early fall. Ideally, a person should get the vaccine before late October.

It is never too late to get the flu shot. Even getting the flu shot in the spring can still protect a person against potential exposure.