I’ve used syringes with the retractable needle on myself hundreds of times. Retractable syringes are usually made by the manufacturer to administer prefilled medication doses - so you don’t have to draw it out of a vial. The reason it’s retractable is so that the person at home who is giving themselves the injection doesn’t have a sharps container and also to help reduce injury from attempting to recap a needle. So the mobile vaccine centers may use these syringes so they don’t have to worry about sharps containers. Also on those syringes with the safety retractable needle - YOU ONLY EVER EVER EVER push the plunger to retract it AFTER you have removed it from the patient. ?‍♀️. I have personally had to educate nurses who have done that to me - it’s very painful. I had one come back into my room and continue to argue with me about it until I pulled up the manufacturers instructions on my phone and showed her in big red letters where it said to not do that. It does explain the weird wrist movement at the end by the nurse in this video, because you have to push the plunger down really hard to release the spring to suck the needle up into the syringe. So at the very least the person giving her the shot is an idiot.