Although naturally occurring smallpox virus was officially declared eradicated in 1980, concern for biological warfare prompted the US Government in 2002 to recommend smallpox vaccination for select individuals. Vaccinia, the smallpox vaccine virus, is administered into the skin, typically on the upper arm, where the virus remains viable and infectious until the scab falls off and the epidermis is fully intact-typically 2-4 weeks. Adverse events following smallpox vaccination may occur in the vaccinee, in individuals who have contact with the vaccinee (ie, secondary transmission), or in individuals who have contact with the vaccinee's contact (ie, tertiary transmission). In June 2014 at Joint Base San Antonio-Lackland, TX, two cases of inadvertent inoculation of vaccinia and one case of a non-viral reaction following vaccination occurred in the security forces training squadron. This includes the first reported case of shaving as the likely source of autoinoculation after contact transmission. This paper describes the diagnosis and treatment of these cases, the outbreak investigation, and steps taken to prevent future transmission.