An immunogenic detoxified protein comprising the amino acid sequence of subunit A of a cholera toxin (CT-A) or a fragment thereof or the amino acid sequence of subunit A of an Escherichia coli heat labile toxin (LT-A) or a fragment thereof wherein the amino acids at, or in positions corresponding to Ser-63 and Arg-192 are replaced with another amino acid. The immunogenic detoxified protein is useful as vaccine for Vibrio cholerae or an enterotoxigenic strain of Escherichia coli and is produced by recombinant DNA means by site-directed mutagenesis.