Hepatitis A vaccine has become one of the main vaccinations for children in China, and some provinces and cities already offer free vaccination against hepatitis A. Currently, there are two main types of hepatitis A vaccines on the market: live attenuated hepatitis A vaccine and inactivated hepatitis A vaccine. The live attenuated hepatitis A vaccine is less expensive, but the inactivated vaccine has better stability than the live attenuated vaccine. When injecting the vaccine, it is best to make sure that you are in good health, otherwise it is easy to develop fever and fail to achieve the therapeutic effect. Injections are all attenuated antigens, and fever can easily occur if the body is not in good condition. At present, 39℃ can be treated with antipyretic drugs and physical cooling. Generally, the fever caused by vaccines is mostly recovered within 2-3 days. A body temperature above 39°C requires oral antipyretic medication. After the fever is reduced, if the temperature rises again for more than 4-6 hours, it can be used once more. If the fever is prolonged, other factors need to be ruled out as the cause and, if necessary, a hospital visit is required. The human body actually tolerates the hepatitis A vaccine well, and most people do not have any adverse reactions to the hepatitis A vaccine after vaccination. A small number of people may experience mild redness, swelling or mild pain at the vaccination site. These hepatitis A vaccine adverse reactions generally subside within 24-72 hours and are considered normal. Very few people may experience malaise, fever, anorexia, diarrhea, nausea, vomiting, allergic rash, etc. These adverse reactions to hepatitis A vaccine are also usually transient and mostly resolve on their own within 24 hours. Generally speaking, mild adverse reactions can be self-resolved without special treatment. In case of severe local reactions, local hot compresses can be applied several times a day for 10-15 minutes after 72 hours. For more severe adverse reactions to hepatitis A vaccine, symptomatic treatment can be given if necessary. For first-time vaccinators, they should stay on site for half an hour after injection to prevent rapid-onset allergic reactions. If there is any abnormal reaction or delayed allergic reaction within 72 hours after returning home, you should go to the hospital as soon as possible to avoid delaying the rescue time.