BCG is not a cowpox vaccine. BCG and cowpox are two different vaccines. BCG is used to prevent the spread of tuberculosis, while cowpox is used to prevent the spread of smallpox. The World Health Organization has declared smallpox extinct worldwide, so there is no longer a need to receive the cowpox vaccine. The BCG vaccine is used to prevent the spread of tuberculosis, which has become a new epidemic worldwide in recent years, so especially in our economically underdeveloped country, all children need to be vaccinated with BCG after birth. Both BCG and cowpox vaccines cause breakage of the inoculation site on the left upper arm, forming a scar, and the BCG scar is called a karst, but BCG and cowpox vaccines are completely different concepts.