A re-closable valve (1, 100, 700, 800) for use in sterile fluid transfer has a body (5) with open entry and exit sides (2, 3) and a passageway (4) for fluid therebetween. The entry side is connectable to an opening of a separate vessel and the exit side is connectable to downstream processing. The entry side includes a first rupturable seal (5b, 500) blocking the opening of the entry side. A piston (9) is connected to an actuator (7) via a cam mechanism (8, 85, 10) which moves the piston (9) axially in the passageway (4) and to the first seal (5b, 500). On movement of the piston (9) during a first actuation, the first seal (5b, 500) is torn free from the entry side to open the valve for fluid transfer. A sharp rim (15) surrounds the opening of the entry side and a curved surface area (193) encircles the piston exterior proximal the entry side. The valve (1, 100, 700, 800) can be re-closed by moving the piston (9) during a subsequent actuation thus engaging the sharp rim (15) with the curved surface area (193) which plastically deform to from a second seal. Arrangements are included to enable the valve (1, 100, 700, 800) to be multiply re-opened and re-closed, if desired.