An aqueous vaccine composition comprises a protein adsorbed on a solid and one or more stabilising agents, wherein the one or more stabilising agents have ionisable groups capable of exchanging protons with the protein and with the ionised products of water dissociation, and wherein the ionisable groups include first groups that are positively charged when protonated and uncharged when deprotonated, and second groups that are uncharged when protonated and negatively charged when deprotonated.
