I used to wear one when i first started. I was afraid i was going to hurt my back. But it turned out to be a nightmare in summer time lol it was like i was walking with a heater around my waist! Terrible! So i started skipping it somedays, until i finally decided i dont really need it. As long as you lift properly using your legs and not your back muscles you will most likely be fine. Plus, you should know the limits of your own abilities, and if you have any doubts about if you can or cannot lift someone, stay safe and dont do it, make sure you get some help.
So, if you really wnat to i guess you could use a back brace just for extra support, but other than that i came to the conclusion that i dont need it.