Studies were conducted delivering the 17D attenuated yellow fever virus vaccine by scarification, but this delivery mode was abandoned as efficacy was low. More recently, a clinical trial compared full dose SC delivery of a 17D vaccine to 1/5 dose delivered ID by Mantoux injection, which found equivalent seroprotection between the two routes (Roukens et al. 2008) . A more extensive description on ID vaccination against yellow fever is provided elsewhere in this special volume on ID immunization (Roukens et al. 2011 ).