It's all very confusing because of no test available and exposed birds that have no symptoms.
Yes, vaccinated chicks can be exposed to Marek's and be carriers, but not die from the disease in 90% of correctly given vaccine.
But unvaccinated chicks can be exposed and carry the disease, but, may at some point die from the tumors. Some of mine were 2 yrs old or more before they died from Marek's. And had it, but never showed symptoms till they died.
So there is no way to tell unless you hatch your own or get vaccinated day old chicks from a hatchery, and have never bought a chick outside that or a chicken from someone.
You can't cull away the disease. If it's on your property , or one of your birds, it's too late.
Greenfire Farms is trying to protect what they sell. If they sell you eggs and you hatch them at home in a bator, and vaccinate them day one and quarantine them for 2-8 weeks (I do 8), those chicks will hopefully not die from Marek's.
If Greenfire farms vaccinates their day old chicks on day one, and you quarantine them for 2-8 weeks, they can get Marek's from your chickens but not die from it. If they sell unvaccinated chicks, it's too late, but I would vaccinate anyway and quarantine. Anyone who sells day old chicks at $100.00 a chick should be vaccinating them immediately to protect their chicks, and their reputation.
So, in a nutshell,
Vaccinate all day old chicks you hatch in your bator on day one and quarantine, or buy day old vaccinated hatchery chicks.
Once it's on your property, culling will not help.
Vaccinating will save your chicks from the tumors only.
Vaccinating is the only way to save your day old little chicks from dying of Marek's.
Always assume your flock has been exposed.