Marek's Vaccine in adult chickens

[Chickenmaven]

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Are your older birds UNvaccinated? I would think that would make a difference.

 

[threehorses]

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I've read that you're not supposed to vaccinate them if they have active (tumorous, or optical) Mareks. But then again I've also read that at the first signs of Mareks that vaccinating them might cause the symptoms to receded and protect them from the harmful parts of Mareks, the tumors and true paralysis.

So what I'd gather from those two bits of information is to not vaccinate one that has tumors or the optical form, but if there's an adult bird in with an active case that starts to show the paralysis, that vaccinating it might keep it from going into the tumor stage.