A dosage delivery device, for example a syringe type device, having a housing (2) defining a reservoir (4); a plunger (6) within the reservoir and movable to decrease the volume of the reservoir so as to discharge material in the reservoir via a discharge opening; and an operating mechanism for the plunger, wherein a closure member (12) seals the discharge opening, and is coupled to the plunger operating mechanism such that it exposes the opening when the mechanism is engaged. In this way, a single movement to prime the mechanism also removes the closure.