Antigen cocktails: valid hypothesis or unsubstantiated hope?

After more than three decades of research into the development of vaccines against parasites, a substantial number of antigens have been identified that, as purified native proteins or recombinant proteins, induce some protection against the target parasite. Very few achieve a degree of efficacy likely to make them candidates for single-antigen vaccines. Therefore, multi-antigen or 'cocktail' vaccines are proposed based on the assumption that such cocktails will show enhanced efficacy. This assumption, although often poorly acknowledged, has become central to much vaccine research. The experimental evidence for it, however, is extremely scarce and contradictory. The efficacy of multicomponent vaccines deserves greater experimental attention than it has received.