Chicks that I order from hatcheries come vaccinated against Marek's disease, a very good thing IMO. Chicks that hatch here aren't vaccinated, so I always have both in my flock. 'Canaries in the coal mine', and so far no Marek's disease here. It's just not true that 'everyone has Marek's disease in their flock'!
It's prudent to feed amprolium medicated feed to chicks for eight to twelve weeks, at least until you have enough experience with your soil and chickens to see if coccidiosis will afflict your chicks. Many of us don't feed the medicated chick starter, because we haven't had chicks sicken and die from this parasite. As a new chicken owner, I'd use the medicated feed. The coccidia 'vaccine' is actually a small dose of coccidia given to each chick, and one day eating the medicated feed wipes it out. I'd leave that vaccine off my list.
Practicing excellent biosecurity pays off! Also, not having close neighbors who bring home sick chickens.
Showing birds puts them at risk for many diseases, and those birds have more testing and vaccines given. Not happening with my birds!
Mary