The two scars on the arm may be from cowpox vaccination or BCG vaccination. 1. Cowpox vaccine: Cowpox vaccine belongs to a kind of protein, which is difficult to be absorbed by the skin after inoculation and can form scars at the inoculation site. Since China stopped vaccinating against cowpox in the 1980s. For people born before 1980, the two scars on the arm are usually left by the cowpox vaccination. 2. BCG: For people born after 1980, the scars on the arms are usually due to BCG vaccination. After BCG vaccination, redness, swelling, ulceration, scabbing and other reactions will occur at the vaccination site. As the ulcers and heal, scars will eventually form, and the formation of scars is one of the signs of a successful BCG vaccination. Scars left by cowpox vaccination or BCG vaccination are usually a normal phenomenon after vaccination and need not be overly worried and do not require special treatment.