Vaccine side effects, or adverse reactions, can be latent for several minutes to several days. The timing of adverse reactions may vary depending on the type of vaccine and the body type of the vaccine recipient. A small number of people may experience significant adverse reactions at the time of vaccination or within 30 minutes, but most people usually have no significant adverse reactions, so there is no need for vaccinees to be overly concerned. After the vaccine enters the body, it takes some time for the immune system to respond to the vaccine before it can take effect and be delivered to all parts of the body through the bloodstream. Vaccinators are advised to stay in the hospital for 30 minutes after vaccination so that any adverse reactions can be dealt with promptly. Symptoms such as redness, swelling, pain, hard nodules, fever, nausea, vomiting, diarrhea, or low-grade fever at the vaccination site within 3 days after vaccination are normal adverse reactions to vaccination. Mild cases can be observed with rest and will generally heal on their own, while severe cases require medical treatment. In addition, you should press the injection site for 5 minutes after vaccination to avoid rubbing the bleeding and causing pain. It is forbidden to take a shower on the day of vaccination to avoid infection caused by water in the needle holes. Avoid eating spicy and allergy-prone foods to avoid triggering or aggravating vaccine reactions. Proper rest and avoiding strenuous exercise can help reduce the occurrence of adverse reactions to the vaccine.