Totally useless for worms. In any case, chicks wouldn't need worming before they are about 18-20 weeks, at POL and about to join the adult flock. At that point, and every 4-6 months after that, give them a 7-day course of Flubenvet. There are various herbal supplements available that claim to tone up the gut so it's more resistant to worm infestation, but none of them actually do the job and kill the worms which all chickens have in their gut to some extent.