The scar on the shoulder generally refers to the scar left by the BCG vaccination, commonly known as the “BCG scar”. Newborns are immunized with BCG to prevent tuberculosis caused by Mycobacterium tuberculosis infection. Generally, redness, swelling and infiltration may appear locally about 2 weeks after BCG vaccination, and then scabs will form after 8 to 12 weeks, which may or may not leave a scar. Different newborns react differently to BCG vaccine, and a few newborns do not leave a scar after BCG vaccination. Different newborns have different scar patterns, mainly normal scar with a diameter of about 4~5mm, 1~2mm needle-point shaped scar, slightly larger protruding scar, scar that is higher than the skin with microvascular dilatation and tenderness, and scabs, etc. Generally, the redness and swelling after BCG vaccination are mild. In general, children with mild redness and swelling after vaccination and no pus have small or no scar; children with pus and ulceration after vaccination have larger scars. If a newborn baby has more pus or even ulcers after BCG vaccination, it should be treated in a regular hospital in time.