With the first set of girls we had, I fed Starter/Grower to some unknown point (probably 2 months, but I can't remember) and then Grower until we collected the first egg, then Layer. With this batch, the girls will be on the starter/grower until the meat chicks are slaughtered and then switch to...
I don't believe you can vaccinate against coccidia, it is prevelant in the system of all dogs, chickens, etc in minimal amounts that are inactive until a stress prompts it to react and start destroying your animal from the inside out.