The present invention relates to a formulation, in particular an aqueous formulation comprising (i) a poxvirus of one of the genera orthopoxvirus, avipoxvirus, parapoxvirus, capripoxvirus and suipoxvirus, (ii) a disaccharide, (iii) a pharmaceutically acceptable polymer and optionally (iv) a buffer. The aqueous formulation is particularly suitable for freeze drying processes resulting in a stable, freeze-dried, poxvirus containing composition. The invention further concerns a method for preparing a freeze-dried, poxvirus containing composition and the thus obtained product.