Stable and effective multivalent vaccine compositions comprising Hepatitis B surface antigen (HBsAg) are described wherein the HBsAg component is stable for one week at 37° C and is highly immunogenic, for example when the vaccine is administered to infants. The compositions typically comprise HBsAg adsorbed to aluminium phosphate and other antigens, especially those suitable for use in a paediatric vaccine, adsorbed to aluminium phosphate or aluminium hydroxide. Methods for preparing the vaccines and the use of aluminium phosphate to stabilise HBsAg in a multivalent vaccine formulation are also described.