If your child has redness and swelling at the site of the injection, a mild rash, or a low-grade fever within a few days of having had a shot, she's probably having a mild reaction to the vaccine. This type of reaction is quite common with many vaccines and nothing to be alarmed about, but check with your doctor if you're concerned.
More severe reactions are rare, but they can happen.
Signs of a serious allergic reaction can include difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, dizziness, fainting, or an erratic heartbeat. This type of reaction will occur within a few minutes to a few hours of the shot if it's going to happen. Call your doctor right away if you notice any of these symptoms. A high fever or a seizure within one to six weeks of a vaccination may also be caused by a reaction to a vaccine, although these symptoms are more likely the result of a virus or bacterial infection. In any case, you'll want to consult your doctor right away to determine the cause and discuss treatment.