Abstract: The invention is related to a hand-operated actuator mechanism for driving a piercing element with increased safety. The actuator mechanism comprises a mounting element connected to a trigger element by a first breakable connection element. It also comprises a piercing element carrier connected to the trigger element by a second breakable connection element. The trigger element further comprises a pushing member that can be pushed with a human finger. The first breakable connection element is configured to be broken by means of a predetermined pushing finger force pushing said pushing member. The piercing element carrier being movable between an initial position wherein the first and the second breakable connection elements are unbroken, and a stop position wherein an abutment stops a movement of the piercing element carrier.