The present invention relates to a vaccine/agonist combination comprising an RNA vaccine comprising at least one RNA comprising at least one open reading frame (ORF) coding for at least one antigen and a composition comprising at least one OX40 agonist. The present invention furthermore relates to a pharmaceutical composition and a kit of parts comprising the components of such a vaccine/agonist combination. Additionally the present invention relates to medical use of such a vaccine/agonist combination, the pharmaceutical composition and the kit of parts comprising such a vaccine/agonist combination, particularly for the prevention or treatment of tumor or cancer diseases or infectious diseases. Furthermore, the present invention relates to the use of an RNA vaccine in therapy in combination with an OX40 agonist.