Mixing vaccinated and non-vaccinated chickens - real life experiences?

[Tristeli]

My first and second group of birds were from hatcheries and vaccinated at birth. A cpl of broody hens hatched out eggs from two of these flock members (obviously I have a rooster). They aren’t vaccinated. Will turn 2yo this summer. Do not have Mareks.

 

[coach723]

There are a lot of people who have mixed vaccination status in their flocks. If you hatch at home, those usually are not vaccinated since most of the vaccines come in huge amounts, not really economical for back yard keepers. And purchased chicks are sometimes purchased with vaccines. And with the Marek's vaccine, to do at home it's really impossible to adequately quarantine them for the required time before they are exposed to the virus. If you have it, it's all over your property and carried on clothing, shoes, equipment, the wind, etc. Marek's can show up really any time. It can be brought in on the wind, it can travel miles, and it can be brought in by wild birds. I have it in my flock. I had chickens for 10 years before it showed up here (no idea how), and I likely missed it with the first couple of birds I lost. It can look like all kinds of things, not just the common paralysis. Whether to vaccinate or not is complicated, emotional, sometimes confusing and some people are adamantly for or against it. I'm not adamant either way, I just made the decision that I'm comfortable with and that works for me. The best thing to do is to educate yourself, learn as much as you can, and then make a decision based on what you think is the best thing for your flock, and for you. We all have slightly different experiences and belief systems, and what works for one may not work for another. If you now, or at some point in the future have Marek's in your flock and want to bring in chicks that are vaccinated, you will need to purchase them at an age where they have had the vaccine long enough before being exposed to the virus, or have a really good plan for not exposing them until that time has passed. If they are exposed too soon, then the vaccine won't be effective. Marek's can change things with keeping chickens, but it's not necessarily the end of the world, or the end of chicken keeping. I know how it feels when it arrives, like you've been hit by a train. But it does get easier to accept and deal with when the panic subsides.
The vaccine itself will not cause your unvaccinated birds to get Marek's. It will prevent many of the vaccinated birds from showing symptoms IF they get the virus, and they CAN still get and transmit it. So IF they GET it, then they can then transmit it to your unvaccinated birds. The vaccine doesn't cause Marek's in any way, it just lets the vaccinated birds live with it, and possibly spread the virus if they contract it. The vaccine doesn't prevent them from contracting the virus, it just prevents the tumors associated with it. I hope that makes sense and clears up some things. I have unvaccinated birds in the 10-12 year old range that have never shown symptoms. Not every bird, even in a Marek's positive flock, will necessarily get sick, even unvaccinated, some of them are more resistant to it, either genetics or individual immune systems. But you have to assume they all have it, they've been exposed, that's why you close your flock and don't sell or give away birds from it. Some strains of the virus are more virulent than others also, so depending on the strain you deal with, losses, especially initially, may be higher than others experience in their flocks. It's pretty variable.