Tap assembly configured to resist release of the tap when an internal vacuum is applied to the tap and to maintain aseptic conditions of fluid within an attached fluid container before first use of the tap. The tap assembly having an actuation member configured to cover at least a portion of a bore within a body; a cover configured to substantially enclose and abut a proximal portion of the actuation member to prevent actuation of the actuation member by engaging with the body; and a piercer element positioned on an end of the actuation member proximal to a sterility membrane sealed over the bore and including at least one projection to pierce the sterility membrane when the actuation member is actuated during first use of the tap assembly.