The present invention relates to an injector comprising a cylinder with a longitudinal axis and an inner wall, a solid piston having a piston body and two or more deformable sealing elements, which deformable sealing elements each abut the inner wall of the cylinder at an abutting interface and seals an annular gap between the piston body and the inner wall of the cylinder, a hypodermic needle attached to an outlet at an outlet end of the cylinder opposite an actuating end of the cylinder, and a piston rod having a tubular section for housing the hypodermic needle, the tubular section having a needle insertion end comprising an engagement device for engaging a complementary engagement device of the outlet or the hypodermic needle, and a needle protection end opposite the needle insertion end, which tubular section comprises a device for actuating the piston, wherein a length of the tubular section is larger than an operating length of the cylinder defined by the distance from the actuating end of the cylinder to the outlet end of the cylinder minus the dimension of the piston parallel with the longitudinal axis. The injector of the invention is suited for delivery of a pharmaceutical composition, such as a vaccine.
