An auto-injection syringe is provided that includes an injection assembly and a retraction assembly operatively securable to the injection assembly. The retraction assembly includes a hypodermic needle having a needle hub, an end cap having a lower seal through which a portion of the hypodermic needle can pass, a retraction spring disposed between the needle hub and the end cap and maintained in a partially compressed condition therebetween, an upper seal urged against a facially sealing surface of the retraction assembly by the force of the retraction spring on the needle hub so that a sealed area is defined between the upper and lower seals, and a vent device in fluid communication with the sealed area for pressure equalization between the sealed area and an exterior of the retraction assembly.
