Vaccination is subjecting the body to a foreign antigenic stimulus that may cause an unhelpful or even harmful immune response in addition to a beneficial anti-infective immune response. In addition to the foreign protein of the vaccine itself, which causes adverse reactions through the immune response, vaccine adjuvants can also cause adverse reactions or allergic reactions. The occurrence and severity of adverse reactions after vaccination are usually related to individual immunity and constitution and vary among individuals. Common adverse reactions to vaccines are as follows: 1. Local symptoms: often caused by drug irritation or allergy, which may manifest as swelling, erythema, papules, herpes, hard nodes, increased skin temperature, itching, pain, swelling of adjacent lymph nodes, etc. in the skin around the injection, and exudation and pus in severe or secondary infections; 2. Systemic symptoms: after absorption of the drug in the vaccine, systemic symptoms may occur through immune or non-immune factors. Such as fever (mostly low fever, body temperature usually does not exceed 38.5℃), headache, dizziness, nausea, vomiting, diarrhea, weakness, muscle aches, drowsiness, lack of energy, loss of appetite, etc. Sometimes, due to the excessive nervousness of the vaccine recipient, he/she may also experience dizziness, manifested as pale face, dizziness, palpitation, chest tightness, fainting and other symptoms. In addition to the above common adverse reactions, severe allergic reactions may also occur in vaccine recipients. Respiratory allergy may manifest as chest tightness, dry cough, laryngeal edema, dyspnea, cyanosis or even asphyxia. Gastrointestinal allergy may manifest as nausea, vomiting, abdominal pain, diarrhea. Anaphylactic shock manifests as hypotension, cold extremities, and skin florid. Asphyxia, laryngeal edema and anaphylaxis are emergencies, and untimely resuscitation may lead to death. Therefore, after vaccination, you should observe closely for 30 minutes before leaving the vaccination site, keep regular rest and rest after returning home, avoid staying up late and ensure sufficient sleep at night. It is recommended to have a light diet, eat less spicy and stimulating food, and avoid smoking and alcohol. It is also necessary to observe the symptoms at home. For mild adverse local reactions, more rest can be taken and the symptoms can be gradually relieved in 2-3 days; if there is high fever, local skin pus and ulceration, allergic rash, limited edema, convulsions and other adverse neurological reactions, it is necessary to promptly seek medical treatment to determine whether the adverse reactions are caused by the vaccine or other lesions.