Injection device with retractable needle

The present invention relates to a needle assembly (1) to be used in combination with a storing device (200) comprising a barrel (8) defining a chamber (9) receiving a product (4) and a piston (2), the assembly (1) comprising: -needle-bearing portion (7) in a first material, movable between an exposed and a retracted positions of the needle (5), -engaging means (8a, 10, 11, 18,) for securing said needle-bearing portion (7) to said barrel (8) in the exposed position, characterized in that it comprises: -sealing means (15) in a second material for tightly sealing the distal end (9a) of said chamber (9) to said needle-bearing portion (7), -a breakable portion (7a) located between said engaging means (8a, 10, 11, 18,) and said needle-bearing portion (7), which, when broken, allows independent proximal displacement of said needle-bearing portion (7) relative to said engaging means (8a, 10, 11, 18,) between said exposed and said retracted positions, said first material being more rigid than said second material. The invention also relates to an injection device (100) comprising said needle assembly (1) and a storing device (200).