Mild problems: • soreness, redness, tenderness, or swelling where the shot was given • fainting (mainly adolescents) • headache, muscle aches • fever • nausea If these problems occur, they usually begin soon after the shot and last 1-2 days.
Severe problems: • Life-threatening allergic reactions to vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the shot.
If the reaction is severe:
What should I look for?