I think this thread has made me even more determined to vaccinate. There are risks with it. Found some great information here:
http://live.psu.edu/story/46250 about vaccinated birds shedding the vaccine's modified strains to other birds, and of course about virus/bacterial evolution. I still think it will be best to vaccinate EVERYONE here, and total bio-security between my flock and others, of course, but also between newbies and the flock until newbies are quarantined, vaccinated and cleared. I know that evolved strains can still be passed for my birds, but I would be devastated if I lost my current flock, but I'm adding a LOT of birds this spring, and will not only have my time, money and energy invested, but quite a bit of money as well. As it is RIGHT NOW, in only my adult flock and counting only hens, I have over $300 worth of birds, and new birds will be more expensive (rarer than just production breeds that I have now). While $300 may not seem like much, it is a lot to me. Our flock was started to keep us as sustainable as possible, GOOD food that is less expensive (ehh, that might be debatable, lol) and we've fallen in love with the flock as a whole and some individuals (I hate to say that I have favorites, but I have several birds that if they were lost, we'd be distraught). So, as it stands now with the research I'm doing, it looks like we'll be vaccinating for everything we can.
I'll have to continue my research, to see if I can sell eggs to non-vaccinated flock owners, or sell my not-yet-vaccinated chicks to other locals and such, and see if vaccinated POL pullets will be restricted to vaccinated flocks only. A big part of our plan was to sell POL pullets to help bring in money, so I've got a ton of research to do yet.