The main object of the present invention is to provide polysaccharide-coated antigens derivatized with lectins for pharmaceutical use. In the vaccines, polysaccharides are preferably selected from the group consisting of chitosan, low-molecular-weight and high-deacetylation-degree chitosan, methyl glycol chitosan, alginic acid, polymannuronic acid and salts or derivatives thereof. In the vaccines of the invention, antigens are microorganisms, infectious agents or constituents thereof, hormones, enzymes, proenzymes, narcotics, bioactive peptides, metabolites, biological precursors, cell constituents, allergens, and the lectins are of vegetable origin.