A method for identifying a vaccine candidate, said method comprising selecting a protein from the proteome of a target organism on the basis of a property selected from a biophysical property or the amino acid composition of that protein. For example, using this method a first set of data for a said property of a one or more vaccine antigens of a particular genus is collected, and a control set of data for said property of one or more random proteins from the same genus is also collected. These datasets are then compared and statistical differences noted. The proteome of a target species may then be examined and one or more vaccine candidates selected from that proteome on the basis that they have a property more similar to that of the first set of data