ABSTRACT
INTRODUCTION Over the last 10 to 15 years, a great deal of effort has been directed toward replacement of existing whole-cell or formalininactivated vaccines with subunit vaccines that may be safer and more effective than existing vaccines. Still other efforts are directed at developing alternatives to traditional vaccine delivery, including mucosal and transcutaneous delivery. It is generally agreed that the latter routes offer a number of potential advantages over traditional vaccines, including (i) elimination of needles and the risk of transferring disease by contamination, (ii) the potential to confer mucosal as well as systemic immunity, (iii) increased stability and perhaps also less of a need for an intact cold-chain, and (iv) that administration would not require trained health care specialists. However, it has become increasingly clear that a major limiting factor for the development of mucosal and transcutaneous vaccines is the availability of safe and, above all, effective adjuvants.
