The present invention relates to an injection needle assembly (10) having opposite distal and proximal ends, comprising: a retainer member (18) configured to be connectable to a medicament container a hub (32) configured to be coaxially displaceable within the retainer member and provided with an injection needle (38) having proximal and distal pointed ends (40 42) and a cap member (12) interactively connected to both the hub and to the retainer member. The invention is characterised in that it further comprises a sealing member (56) arranged between said cap member (12) and said retainer member (18) for preventing contamination of said injection needle (38) before use.
