Q: My hen was vaccinated for Marek's disease as a chick, but I still lost her to this illness. How could this have happened?
A: Marek’s disease is very common and will eventually end up in most backyard flocks, whether or not the flocks have been vaccinated. It's strange but true! The Marek’s vaccination helps prevent some of the most severe symptoms of Marek’s disease, but does not prevent the actual transmission of the virus. The vaccine is very effective, but not 100% foolproof, which means a small percentage of vaccinated chickens might still succumb to the symptoms and die.
Since the Marek’s vaccination prevents tumors in over 90% of vaccinated chickens who are exposed to Marek’s, we highly recommend getting your chicks vaccinated at hatch. Chicks should be vaccinated as soon as possible after hatching because the vaccine is not effective when given to chicks already exposed to Marek’s disease.
In order to increase the effectiveness of the vaccine, keep your chicks indoors and away from all other birds until the chicks are 14 days old, at which point the vaccine will have started to take effect. Make sure you wash your hands and change clothes after handling other poultry, so that you don’t infect your newly hatched chicks before they are protected by the vaccine.