I don't vaccinate my chickens, and won't. They are not closed vaccines, don't do what they claim, and give a false sense of security. In addition, a couple of the chicken diseases would have probably been eradicated by now, instead of mutating to several strains, had it not been for open chicken vaccines.
There's a lot of mis-information out there about vaccines. I think the choice is clearer for me because my flock is Marek's exposed and my #1 concern is preventing my chicks/chickens from dying from Marek's. I know there's a lot more that we desire from a vaccine , but it's just not there at this time.