Source: U.S. Centers for Disease Control and Prevention (CDC). Available online: http://www.bt.cdc.gov

The pictures show a typical reaction to the smallpox vaccine. First, a small bump (papule) forms at the vaccine site 3 to 5 days after vaccination. This becomes a pus-filled area (pustule) a few days later. The pustule dries up and then forms a scab by about 14 days after vaccination. The scab finally falls off at about 21 days after vaccination.