BCG vaccine usually requires only 1 vaccination and the latest vaccination time cannot be generalized. Under normal circumstances, only one BCG vaccination is needed, which should be given within 24 hours after birth. After the vaccination, it is necessary to check whether the vaccination is successful or not 3 months after birth, and if it is not successful, it is necessary to make up the vaccination. If for some reason the BCG vaccination is not given within 24 hours after birth, it can be postponed until 3 months after the situation has stabilized. If vaccination is not given within 3 months, it can be postponed until 3 years of age. However, a tuberculin test is required before vaccination within 3 months to 3 years of age. If the result is negative, vaccination is allowed; if the result is positive, vaccination is not allowed; and 4 years of age and above cannot be vaccinated again. BCG vaccine belongs to the first class of China’s planned immunization vaccine, can be free of charge, mainly used for the prevention of tuberculosis, parents need to vaccinate their babies in time.