A hypodermic needle assembly configured such that the movement of a needle shield into position to block the needle tip occurs as a direct consequence of a longitudinal force applied by insertion of a syringe plunger is provided. The hypodermic needle assembly according to the present invention comprises a needle, a needle hub, and a safety spring clip assembly, the safety spring clip assembly being configured to automatically launch from the needle hub and slide along the needle until the spring clip meets a needle stop at the needle tip, thus preventing the guard from being removed from the needle shaft. A method of using the hypodermic needle assembly according to the present invention is also provided, which includes the method of launching the spring clip with a syringe having multiple advancing mechanisms.