The invention provides for a method of enhancing immunological responses to an antigen in a vaccine formulation, and for a vaccine formulation that provides for an enhanced immunological response to an antigen. In the method and formulation the antigen is administered with an adjuvant which adjuvant comprises a solution of nitrous oxide gas in a pharmaceutically acceptable carrier solvent for the gas and which adjuvant includes at least one fatty acid or ester or other suitable derivative thereof selected from the group consisting of oleic acid, linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid [C20: 5ω3], decosahexaenoic acid [C22: 6ω3], ricinoleic acid and derivatives thereof selected from the group consisting of the C1 to C6 alkyl esters thereof, the glycerol-polyethylene glycol esters thereof and the reaction product of hydrogenated natural oils composed largely of ricinoleic acid based oils, such as castor oil with ethylene oxide.