Auto-injector for administering a dose of a liquid medicament, comprising: - a chassis containing a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the auto-injector having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the chassis, - a drive spring capable of, upon activation: - pushing the needle from a covered position inside the chassis into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - retracting the syringe with the needle into the covered position after delivering the medicament, - activating means arranged to lock the drive spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the drive spring for injection, wherein the drive spring is a compression spring arranged to be grounded at a distal end in the chassis for advancing the needle and for injecting the dose of medicament via a plunger and wherein the drive spring is arranged to have its ground in the chassis switched to its proximal end for retracting the syringe, wherein a retraction sleeve is axially movable arranged around the syringe, wherein the retraction sleeve is fixable to the chassis in a maximum proximal position for providing ground at the distal end of the drive spring, wherein the retraction sleeve is arranged to take the syringe with it when released and translated in distal direction, wherein the drive spring is wrapped over the retraction sleeve with its distal end bearing against a thrust face on the retraction sleeve and with its proximal end bearing against a thrust collar arranged to be coupled to the plunger for joint axial translation for advancing the needle and for injecting the dose of medicament and wherein the thrust collar is arranged to be decoupled from the plunger for retraction, wherein the activating means is arranged as a trigger button in the shape of a wrap-over sleeve button arranged over the distal end of the auto-injector, the trigger button extending at least almost over the whole length of the auto-injector, wherein the trigger button is arranged to release the drive spring upon translation in proximal direction characterized in that an interlock sleeve is telescoped with the proximal end of the chassis and with the trigger button, the interlock sleeve translatable in longitudinal direction between a proximal position relative to the trigger button and a distal position relative to the chassis and biased towards the proximal position, wherein the interlock sleeve is arranged to release the retraction sleeve when in the proximal position and with the trigger button translated in proximal direction and wherein the interlock sleeve is arranged to block the translation of the retraction sleeve otherwise. - a chassis containing a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the auto-injector having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the chassis, - a drive spring capable of, upon activation: - pushing the needle from a covered position inside the chassis into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - retracting the syringe with the needle into the covered position after delivering the medicament, - pushing the needle from a covered position inside the chassis into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - retracting the syringe with the needle into the covered position after delivering the medicament, - activating means arranged to lock the drive spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the drive spring for injection, wherein the drive spring is a compression spring arranged to be grounded at a distal end in the chassis for advancing the needle and for injecting the dose of medicament via a plunger and wherein the drive spring is arranged to have its ground in the chassis switched to its proximal end for retracting the syringe,