your child may be experiencing an unusual condition such as a high fever weakness or behavioral changes that are particularly concerning to the parent such as unresponsiveness. additionally signs of a serious allergic reaction may include difficulty breathing hoarseness or wheezing hives weakness a fast heartbeat or dizziness. if you suspect a serious reaction then contact a doctor right away or take the child to an emergency department to be checked urgently.
how will i know if my child is having a bad reaction [to a vaccine]?