Inclusion of fatty adjuvants in vaccine compositions can cause difficulties with certain antigenic components, particularly with antigens that include a surfactant component. A method for preparing an immunogenic composition comprising an antigen and a fatty adjuvant involves purification of the antigen substantially in the absence of surfactant. Where surfactants cannot be avoided, the following are combined: (i) an antigen component that includes a surfactant and (ii) a fatty adjuvant component, to give a composition in which the weight ratio of said fatty adjuvant to said surfactant is less than 1000:1.
