A process for producing an embedded protein antigen,comprising embedding a protein antigen having two or morecysteine residues in a molecule thereof, into ahydrophobized polysaccharide. Prior to or after theembedding of the protein antigen, the protein antigen ispurified. There are provided an embedded protein antigenand a process for producing the same, which canadvantageously purify the protein antigen, whilesuppressing the denaturation of the protein antigen ascompletely as possible.
