The invention relates to pharmaceutical compositions comprising replication-defective adenoviruses, said adenoviruses generally comprising an adenoviral genome wherein a heterologous nucleic acid of interest is incorporated, and wherein said nucleic acid typically encodes an antigen. Such compositions are suitable for vaccination purposes. The pharmaceutical compositions of the present invention further comprise an adjuvant, which stimulates and increases the immune response towards the antigen encoded by the heterologous nucleic acid. Preferred adjuvants are oil-emulsion based adjuvants and aluminium-based adjuvants.
