You don't ask easy questions, do you? But they are good questions.
Whether to worm or not is a personal preference. Some of us treat or medicate when we see a problem. Some people worm on a regular schedule. It is just up to you.
You could write a book on vaccinations. There are several different things you could vaccinate for. In my opinion, which you do, if any, should be based on your experiences and the conditions around you. When I was looking into it, there had been one reported case of Marek's in this county in the previous two years. I elected to not vaccinate for Marek's. My county extension agent hooked me up with a university Ag professor that teaches chicken diseases, breeds chickens for show, and is on the team that responds to reported outbreaks of poultry diseases in this area. After discussing how I planned ot manage my chickens, he recommended that I not vaccinate for anything. I keep a closed flock. I do not bring in other chickens, except hatchery chicks that are extremely safe, and I do not show my chickens. So they are not exposed that much. Depending in how you plan to manage your chickens, the answer may be totally different for you. I think it is helpful for us to tell you what we do, and really helpful if we say why, but our conditions are not the same as yours. Our answers may be different.
Some people do all sorts of weird and glorious things as a preventative. I don't. I try to keep the coop, run, and brooder dry, watch for problems, make sure they have appropriate food, water, and shelter, and treat only when necessary. Others take a totally different approach. Most of us have pretty healthy chickens. As with most things chickens, there is seldom any one right answer that covers us all.
Anyway, this is my opinion. Others will hopefully weigh in with different responses. Good luck!
