Anti-glucan antibodies have been found to be protective against systemic fungal infection with C. albicans, but the protective efficacy can be inhibited by blocking antibodies. The invention provides an immunogenic composition comprising a glucan and a pharmaceutically acceptable carrier, characterized in that, when administered to a mammalian recipient, the composition elicits protective anti-glucan antibodies but does not elicit antibodies which inhibit the protective efficacy of the anti-glucan antibodies. The glucan may be presented on the surface of a protease-treated microbial cell or may be presented as a protein-glucan conjugate. The glucan may be substituted by a glucan mimotope, a peptidomimetic of a glucan mimotope, or nucleic acid encoding a mimotope. Anti-glucan-antibodies show broad spectrum microbicidal activity. β-glucans are preferred, particularly those containing one or more β-1,6 linkages.