What about people who get a seasonal flu vaccine and still get sick with flu-like symptoms?

There are several reasons why someone might get flu-like symptoms even after they have been vaccinated against the flu.

  • People may be exposed to an influenza virus shortly before getting vaccinated or during the two-week period that it takes the body to gain protection after getting vaccinated. This exposure may result in a person becoming ill with flu before the vaccine begins to protect them.
  • A person may be exposed to an influenza virus that is not included in the seasonal flu vaccine. There are many different influenza viruses that circulate every year. The flu shot protects against the 3 or 4 viruses (depending on whether the flu shot is a trivalent or quadrivalent vaccine) that research suggests will be most common.
  • Unfortunately, some people can get infected with an influenza vaccine virus despite getting vaccinated. Protection provided by influenza vaccination can vary widely, based in part on health and age factors of the person getting vaccinated. In general, the flu vaccine works best among young healthy adults and older children. Some older people and people with certain chronic illnesses may develop less immunity after vaccination. However, even among people who tend to respond less well to vaccination, the flu vaccine can still help prevent influenza. Vaccination is particularly important for people at high risk of serious flu-related complications and for close contacts of high-risk people.

Show All Answers

1. What is seasonal flu?
2. How can I protect myself and my family from the flu?
3. Who should get vaccinated this season?
4. How effective is the flu shot?
5. What are the risks from getting a flu shot?
6. What are the side effects that could occur?
7. Can the flu shot give me the flu?
8. Why do some people not feel well after getting the flu shot?
9. What about people who get a seasonal flu vaccine and still get sick with flu-like symptoms?