A method for manufacturing recombinant neuraminidase by culturing in a suitable culture medium host cells which are transformed with a neuraminidase expression vector or infected with a virus which is transformed with a neuraminidase expression vector, wherein the expression vector comprises at least a part of the coding region of a neuraminidase gene of an influenza virus minus the region which codes for the membrane anchor, or a modified version thereof, preceded in phase by a signal sequence; and isolating the expression product neuraminidase from the culture medium. The invention further relates to vectors expressing the neuraminidase.