Intradermal delivery of vaccines: potential benefits and current challenges

Most vaccines are delivered by the intramuscular or subcutaneous routes using a needle and syringe; the intradermal route is only widely used for the administration of Bacille Calmette-Guérin and rabies vaccines. However there is renewed interest in intradermal vaccine delivery, driven by the fact that the dermis and epidermis of human skin are rich in antigen-presenting cells, suggesting that delivery of vaccines to these layers, rather than to muscle or subcutaneous tissue, should be more efficient and induce protective immune responses with smaller amounts of vaccine antigen. Clinical trials investigating intradermal delivery and its potential for dose-sparing have been conducted with several different vaccines, with variable results. These have been reviewed in a recent report from the Program for Appropriate Technology in Health (PATH) and the World Health Organization (WHO).2 For some vaccines, there has been a clear demonstration of dose-sparing by intradermal delivery; however, there are several gaps in knowledge as well as developmental and operational challenges to overcome if the benefits of using intradermal delivery are to be fully realized.