A novel approach to coated microneedles involved the use of polyphosphazene (PCPP), which served as both an effective coating excipient and an immune adjuvant ). ID microneedle immunization with hepatitis B surface antigen (HBsAg) in pigs using the PCPP coating formulation was superior in inducing antigen-specific IgG compared to ID injection by hypodermic needle with or without PCPP. Another study demonstrated effective generation of cellular immune responses to a hepatitis C DNA vaccine administered to mice using coated microneedles (Gill et al. 2010) . Other studies have sought to specifically target delivery to antigen-presenting Langerhans cells using extremely short (*100 lm) needles that penetrate only into the epidermis. These short needles were coated using a novel coating process involving gas-jet drying (Chen et al. 2009 ). In an initial study, vaccination with ovalbumin-coated needles induced similar immune response to IM immunization. In a follow-up study, microneedles coated with a low dose of hemagglutinin-based influenza vaccine generated a similar immune response as IM vaccination at a 100-times larger dose. The authors proposed that these short, densely packed microneedles could deliver more than half of the antigen directly to antigen-presenting cells such as epidermal Langerhans cells and dermal dendritic cells (Fernando et al. 2010) .