The adverse reactions of BCG vaccine are divided into common adverse reactions, rare adverse reactions and extremely rare adverse reactions. Common adverse reactions include the following: 1. local redness and swelling infiltration can appear about 2 weeks after vaccination, followed by pus formation of small ulcers, and scabs after 8-12 weeks, which generally do not require treatment, but need to pay attention to local cleanliness to prevent secondary infection; 2. pustules, superficial ulcers and those with secondary infection should be treated by a doctor at the hospital; 3. local abscesses and ulcers with a diameter of more than 10 mm, and long-term If the diameter of local abscesses and ulcers exceeds 10mm, and if they do not heal for a long time, they need to be treated promptly; 4.The reaction of lymph nodes, the axillary lymph nodes on the inoculation side can appear slightly enlarged, usually not more than 10mm, and will subside after 1-2 months. If the local lymph nodes are swollen and softened and pustules are formed, it is necessary to go to the hospital for timely consultation and treatment; 5. Transient febrile reactions can occur after vaccination, most of which are mild febrile reactions that can be relieved by themselves after 1-2 days and generally do not require treatment. Rare adverse reactions include severe lymph node reactions and occasional keloids when replanting. Very rare adverse reactions include osteomyelitis, allergic rash, and allergic purpura.