Hm... but these chicks aren't "perfectly fine" one minute and dead the next. They stop eating and drinking and waste away, peeping a lot the last day. Mary did say that her Isbars came straight from GFF and were probably Marek's vaccinated. So they are the grandparents of my chicks and I'm not really sure that it would carry that far, plus the Isbars are being brooded by themselves now and still dying. I'm fairly certain Jordan Farms stock also came from GFF and would have been vaccinated also but I don't know how many generations before they got to me. Hm.... worth a little more research. I will definitely post when I get more information from the lab.