Why are you having a reaction after taking a flu shot?

Answer 1

Many people do get a local reaction to the flu shots. It is the body responding to the presence of the virus that was in the vaccine. This immune response is exactly why you get the vaccination. The body recognizes the invading virus as foreign and sends the attack team to the rescue. The soreness and tender red area should be gone in a few days, if not, then you may need to be sure there is not a local infection from the needle by having it examined by a health care professional.

Usually, even though it seems the wrong thing to do at the time, if you use the muscle where the injection was given, the soreness will go away faster. I ask for my flu shots in my right arm to force myself to use it since I am right handed and now that I've started doing that, I have much less soreness after my flu shots and the soreness lasts a shorter time period.

If you are talking about a reaction that is not localized, as in an allergic reaction with lip, tongue or facial swelling or trouble breathing, then you need to get urgent medical attention since it could be you are allergic to eggs or some other component of the vaccine.

Answer 2

You may have a mild reaction to the vaccination at the local injection site making your arm sore and a little red. Some people also get a slight systemic reaction with very mild symptoms of the flu. It is because the vaccine is doing what it is supposed to do, triggering the immune system to react as if you were exposed to the active virus in the environment. These mild symptoms are usually gone in 2-3 days if you get them at all.

You don't get sick with the actual flu, however, since there is an inactive virus in the shot. The nasal mist does have weakened but alive virus particles in it. It is possible for people with very compromised immune systems to get the virus from that type of vaccination or from someone else who has just received the vaccine in a nasal mist, although that is a very rare occurrence. People in that state of severe malfunction or suppression of the immune system are advised against taking the live virus vaccines, and also to stay separated from others who have just had that type of vaccine.

See the related question below for information about catching the flu from the flu shot. You don't, unless as mentioned above, you are among the severely immuno-suppressed group.