Why do I feel sick after getting a flu shot?
The most common side effect of the flu vaccine in adults is soreness at the spot where the shot was given, which usually lasts less than two days. The soreness is often caused by a person’s immune system making protective antibodies to the killed viruses in the vaccine. These antibodies are what allow the body to fight against flu.

The needle stick may also cause some soreness at the injection site. According to the Advisory Committee on Immunization Practices (ACIP), rare symptoms include fever, muscle pain, and feelings of discomfort or weakness. If these problems occur, they are very uncommon and usually begin soon after the shot and last 1 to 2 days.

Show All Answers

1. How do I know that I have the flu?
2. How does the flu spread?
3. How long is a person with flu virus contagious?
4. Can the flu be treated?
5. Why should people get vaccinated against the flu?
6. When should I get a flu vaccine?
7. How do flu vaccines work?
8. Is the “stomach flu” really the flu?
9. How many people get the flu each year?
10. Do other respiratory viruses circulate during the flu season?
11. How soon will I get sick if I’m exposed to the flu?
12. How do scientists determine which strains to protect against in a flu vaccine?
13. Can a flu vaccine give you the flu?
14. Why do I feel sick after getting a flu shot?
15. Why did I still get sick even after I got a flu shot?
16. Do I need to get a flu vaccine every year, or will the immunity carry over from last year’s vaccine?
17. Is it ever too early or too late to get a flu vaccine?
18. How can I learn more about the progress of the flu season?