- Vaccinia (smallpox) vaccine determined by (1) clinical evidence of vaccinia scarification; (2) self-reported history of vaccinia vaccination; (3) date of birth; or (4) U.S. military service prior to 1989 or after December 2002 (not excluded: a participant born before 1975, or with past U.S. military service, who self-reports he/she did not receive vaccinia vaccine and has no evidence of scarification)