The present invention provides methods and systems for recovering an essentially cell-associated expression product from a host cell comprising (a) culturing said host cell under conditions that allow expression of said expression product; (b) collecting said host cell in/on a filter unit; (c) disrupting said host cell in/on the filter unit; and (d) separating said expression product from said disrupted host cell. The present invention also provides an expression product obtainable by the methods or systems, wherein the expression product is a poxvirus.