The present invention relates to an injection device for delivering a plurality of doses of a liquid drug. The injection device comprises a housing assembly (10,110,210) and a needle mount (11,111,211) securing a needle cannula (32,132,232). The distal end of the housing assembly is covered by a removable protective cap assembly (50,150,250) when not in use. The protective cap assembly also surrounds a distal tip of the needle cannula and is operational sealed against the housing assembly with an air-tight seal such that an air-tight chamber (60,160,260) is established around the distal tip of the needle cannula between injections.
