Mass vaccination: solutions in the skin.

The skin is populated with Langerhans cells, thought to be efficient, potent antigen-presenting cells, that are capable of inducing protective immunity by targeting antigen delivery to the skin. Delivery to the skin may be accomplished by active delivery such as intradermal injection, use of patches or a combination of a universal adjuvant patch with injections. The robust immunity induced by skin targeting can lead to dose sparing, novel vaccines and immune enhancement in populations with poorly responsive immune systems, such as the elderly. Vaccine delivery with patches (transcutaneous immunization), may allow self-administration, ambient temperature stabilization and ease of storage for stockpiling, leading to a new level of efficient vaccine distribution in times of crisis such as a bioterror event or pandemic influenza outbreak. The use of an adjuvant (immunostimulant) patch with injected vaccines has been shown in clinical studies to enhance the immune response to an injected vaccine. This can be used for dose sparing in pandemic influenza vaccines in critically short supply or immune enhancement for poor responders to flu vaccines such as the elderly. Transcutaneous immunization offers a unique safety profile, as adjuvants are sequestered in the skin and only delivered systemically by Langerhans cells. This results in an excellent safety profile and allows use of extremely potent adjuvants. The combination of the skin immune system, safe use of potent adjuvants and ease of delivery suggests that skin delivery of vaccines can address multiple unmet needs for mass vaccination scenarios.