A vial adapter for a needle-free injection syringe and methods of filling a needle-free syringe from a vial of injectable fluid. One vial adapter embodiment includes a housing and a compliant valve. The housing includes a central divider located between a vial opening and a needle-free syringe opening. The housing also includes a hollow center post extending from the central divider toward the needle-free syringe opening and a hollow filling needle extending from the central divider toward the vial opening. Together, the filling needle and center post provide for fluid communication between the vial opening and the needle-free syringe opening. The compliant valve includes a surface forming a fluid tight seal with the central divider and an inner passageway. In addition, a syringe sealing surface provides for a fluid tight seal with a needle-free syringe placed into contact with the compliant valve. The compliant valve includes an opening in the syringe sealing surface which is biased closed when no needle-free syringe is engaged with the vial adapter and which is opened when a needle-free syringe is fully engaged with the opening.