A retractable safety syringe may have a needle, needle holder, syringe body, and a plunger assembly. A proximal portion of the body and a piston of the plunger may define a vacuum chamber. The plunger assembly may comprise a distal piston and a proximal piston, with an intermediate chamber disposed between the two plungers. A vent through the syringe body pneumatically connects ambient air and the intermediate chamber allowing air to escape out of the intermediate chamber when a plunger assembly traversed toward the engaged position and allow air to be introduced into the intermediate chamber. A retraction force may be created by the vacuum chamber by traversing the plunger assembly to the engaged position. At the engaged position, the distal piston may engage the needle holder and the retraction force may retract the needle holder and needle into the syringe body to prevent accidental needle pricking and needle reuse.