In PMED, gold beads 1-3 lm in diameter are coated with vaccine and delivered by needle-free jet injection into the epidermis. This approach may be particularly suited to DNA vaccines, as deposition of coated particles into the stratum corneum and epidermis may encourage DNA uptake and expression by resident antigen-presenting cells. DNA vaccines for hepatitis B delivered by PMED have induced protective antibodies (Roy et al. 2000; Roberts et al. 2005) . Clinical studies have also been conducted with DNA vaccines for seasonal influenza to evaluate the feasibility of this approach. Results have been promising, but immune responses are not yet equivalent to standard vaccine delivery methods (Drape et al. 2006; Jones et al. 2009 ). EPI and PMED delivery of DNA vaccines for a variety of other diseases have also shown immunogenicity preclinically, including malaria, avian influenza, herpes simplex virus, HIV, non-small cell lung cancer, Eurasian encephalitic viruses, hantaviruses, SARS coronavirus, and smallpox (Weniger and Papania 2008) .