Figure 2. Schematic overview of different approaches to increase skin permeability.
A. Intact skin. B. Stratum corneum (SC) disruption (indicated by white space in figure) leads to better transport of vaccine molecules. C. Partial or complete removal of SC leads to reduction or elimination, respectively, of transport barrier. D. Direct penetration across SC bypasses the barrier layer as exemplified with jet injector and microneedles as representative examples.
D: Dermis; SC: Stratum corneum; VE: Viable epidermis.