Needle-free jet injectors create a fine stream of pressurized liquid that penetrates the skin. The depth of delivery-ID, SC, or IM-is largely determined by design variables such as the injection stream coherence, quality, and pressure; orifice size, skin and tissue thickness, and the angle of the injection relative to the skin (Schramm-Baxter and Mitragotri 2004; Weniger and Papania 2008) . Vaccines that have been shown to achieve immunity when administered via jet injection to conventional depths (i.e., ID, SC, or IM, depending on the vaccine) include typhoid, cholera, BCG, tetanus-diphtheria for adults, whole cell diphtheria-tetanus-pertussis (DTP), measles, meningococcal A and C, smallpox, yellow fever, hepatitis A, hepatitis B, influenza, plague, polio, and tetanus (Weniger and Papania 2008) .