A safety needle device for a medical injector supporting a needle projecting forwardly from the front of the injector body has a tubular sleeve for a supported needle, the sleeve being slidable rearwardly with respect to the needle to expose at least the tip thereof. The sleeve has a forward end for contacting an injection site and a removable cover is engaged in sealing contact with the forward end of the sleeve. The sleeve may have an in-turned flange at its forward end defining an orifice through which the needle projects when the sleeve slides rearwardly. The removable cover may effect a seal to that flange.