Mareks is everywhere. If you have air on your property, it's there. Some breeds are highly vulnerable to it (ex. Silkies) and others are fairly resistant.
So the birds I have that are from a hatchery are they vaccinated ?
Not unless you ordered them from the hatchery and paid the extra for vaccination.
I don't stress on the hatchery layers I get. I did loose two of the buckeyes to it last year.