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Medicated feed doesn't actually protect against cocci, but helps. It's designed to allow the birds to have a little exposure to cocci so that they develop their own immunity without coming down with the actual illness.
I hadn't heard that about the cocci vaccine and medicated food, but it makes sense I suppose.
And incidentally, chickens can still get coccidiosis even if vaccinated. The vaccine contains three of the most common of about eight cocci species, the ones your bird are most likely to encounter. However, if they encounter enough cocci oocysts to overwhelm the vaccine (in warm wet conditions, not very clean conditions, or if their beneficial bacteria in the gut are overwhelmed) they can still get it. So you want to pay careful attention to those conditions and eliminate them from your raising pens.
As for your babies, you could vaccinate for both. However, raising the babies all with probiotics can help with preventing coccidiosis if you keep the brooders all good and dry and clean. I'd use medicated feed for the hatchlings and not put them together in case your new babies shed oocysts from their vaccine (don't know if that's possible). They should be apart anyway for a good while. Your hatched babies can carry things vertically transmitted.