The possibility of dose sparing enabled by ID vaccination has been suggested by previous preclinical and clinical studies; however, the successful application of this approach has yet to be definitively confirmed for many vaccines (Glenn and Kenney 2006; Lambert and Laurent 2008; Nicolas and Guy 2008) . Although the conclusions vary between different studies and different vaccines, there is an indication that dose sparing may be possible. However, it is not currently clear under what conditions the skin's unique immune environment can be harnessed for optimal effect. In addition to dose sparing, there is preclinical study evidence of other beneficial differences of ID vaccination. Studies with microneedles showed improved influenza virus clearance from the lungs and enhanced memory responses compared to IM vaccination (Kim et al. 2011) . Studies with EPI showed a specific role for Langerhans cells to generate robust antibody responses . Studies with ultrasound-mediated vaccination suggested an adjuvant effect on the skin (Dahlan et al. 2009 ).