The hepatitis A vaccine is made from inactive virus and is quite safe. In general, there are very few side effects. The most common potential side effect is soreness at or around the injection site. Other potential side effects include mild headache, loss of appetite among children, and feeling tired. These side effects usually last 1 or 2 days. However, like any medicine, the vaccine could cause serious problems, such as an allergic reaction, which may appear within a few minutes or hours after getting the shot. This occurs very rarely, but if you believe you are having a reaction to the vaccine you should call your provider right away. Some warning signs of a serious allergic reaction include the following:

• High fever
• Behavior changes
• Difficulty breathing
• Hoarse voice or wheezing
• Hives
• Pale skin
• Weakness or dizziness
• A fast heart beat