Not everyone will experience discomfort after the injection of the new crown vaccine, but a small number of people may experience various adverse reactions and allergic reactions. The time of occurrence of different adverse reactions and allergic reactions varies. 1. Local adverse reactions: relatively common, usually occurring at the time of vaccination or a few hours after vaccination, manifesting as local redness, swelling, hard nodules, itching, pain, and, in rare cases, lymphadenitis or swollen lymph nodes; 2. Gastrointestinal reactions: mostly occurring within half to three days after vaccination, with symptoms such as loss of appetite and nausea, which usually do not require special treatment; 3. 3. Allergic rash: usually occurs within a few hours to a few days after the injection of the new vaccine and is characterized by urticaria or maculopapular rash on the face, behind the ears, trunk, limbs and other parts of the body, mostly in the form of a red rash with obvious itching. Allergic people are prone to it; 4. Angioneurotic edema: usually occurs within 24 hours of injection of the new crown vaccine. It shows local redness and swelling of the injection, and the scope gradually expands, which may cause redness and swelling of the whole upper arm, and may even extend to the face, and may be accompanied by urticaria in other parts of the body, but the chance of appearing is low; 5, systemic reaction: fever generally appears 6-24 hours after vaccination, and the general temperature is around 37.5℃, and may also cause headache due to fever, which usually does not require special treatment and can naturally subside within 2-3 days; 6 Anaphylactic purpura: generally occurs 2-7 days after the injection of the new crown vaccine, manifested as rash, bleeding spots, bleeding spots, may be accompanied by joint pain, the chance of occurrence is low; 7, anaphylaxis: the incidence is also low, generally at the time of injection of the new crown vaccine or a few minutes to 45 minutes can occur. Patients show a drop in blood pressure, cold extremities, generalized itching and cyanosis, and if there is laryngeal edema, it may also show chest tightness, breath-holding, difficulty in breathing and suffocation, etc. If the resuscitation is not timely, it may be life-threatening. Therefore, in order to avoid critical situations, it is necessary to observe at the scene for 30 minutes after vaccination.