Chicks vaccinated for Marek's more at risk for cocci outbreak?

[QuailQT]

I just recently bought chicks from a reputable breeder, (not a hatchery). They asked if I would like them vaccinated for Marek's. though I've never vaccinated any of my other chicks that I've hatched in the last 5 years, I thought what could it hurt?
I think that I made a mistake in doing that. Did I not just introduce it into my whole flock? Now I'm reading that Marek's will be shed through their feathers and dander for the rest of their lives. Will it be enough to make the rest of my unvaccinated birds sick?

Also, I've never had an outbreak of coccidiosis where it was causing bloody stools and deaths. Just a couple days ago, I noticed large amounts of bright red bloody poo in one of my grow out pens...the pen that has the vaccinated chicks. Is it just a coincidence?? Or could it be that the vaccine has lowered their immunity a bit and now they are having trouble keeping the cocci at a reasonable level? (Kind of like when you go to the doctor, get a vaccine for something and then you end up getting sick with something else that you caught while at the doctors office.) The other two grow out pens with chicks that weren't vaccinated haven't been affected yet. (Keeping fingers crossed they don't. I'm treating them all with Corid, just in case) .

Has anyone else noticed anything like this?

 

[Folly's place]

Marek's vaccine does not cause disease either in the vaccinated or the unvaccinated birds. Never. Coccidiosis is a totally separate problem, maybe just your first outbreak, if that's what the problem actually is. Having a fecal checked will answer that question, and then treating as needed will work. New chicks experience a lot of stress, and the vaccinations can be the least of it. Hope everyone recovers well. Mary