Are vaccines 100% when it comes to illnesses. Such as MG and mereks

[Ridgerunner]

I don't think the US has a salmonella vaccine. At least, not one available to anyone besides factory farms. I've only seen mareks and Newcastle options when I get mine

I've seen a vaccine for Coccidiosis in the USA at some hatcheries, but that's only for certain strains, not all of them.

 

[Ridgerunner]

Antibodies produced from having received a vaccine are not passed on to offspring.

I don't think it proves anything but for plants to be considered "organic" the seeds have to be produced by organic plants. To be considered organic, chickens do not need to come from organic parents. With poultry what matters is what happens after they hatch (food, medication, etc). With mammals it's a little different, the mother has to be managed organically for the last 1/3 of gestation.

I think the offspring not being able to share body fluids so they cannot pass down certain things is at last one reason why poultry "organic" rules are set up this way.

Then the disclaimer. This is USDA rules for the USA only. I have no idea how Canada, European Union, UK, Australia, or anywhere else are set up. The different requirements for different countries or jurisdictions create a lot of confusion on this forum on many different topics.

I got two chickens yesterday that are vaccinated for those two diseases. Both diseases are on my property

I agree with the others, nothing in nature is 100% effective. Marek's vaccine doesn't claim to be. That vaccine doesn't prevent the chicken from getting Marek's if it is exposed to it. It can spread the disease if it catches it. The vaccine greatly reduces the chance that the tumors that cause the harm from forming so the risk of any damage is tremendously reduced.