Day old chicks are vaccinated for what!? Well, thankfully not ours.

I was chatting with someone recently who casually mentioned to me how great buying day old chicks from a hatchery is, because they come to the farm already vaccinated. Wait. What!? This caught me by surprise… but it really shouldn’t have. I mean, we vaccinate day old human babies. Of course day old chicks are, too! I had to learn more. 

The first thing I did was called the hatchery where Miller Bio Farm’s chicks come from. They told me that, at some hatcheries, vaccination is routine. But, at theirs, it is by request only. And this year they are choosing to not offer vaccination at all.

It’s common for day old chicks to be vaccinated for Marek’s disease. 

Marek’s disease is a Herpes-like virus that, once diagnosed, is untreatable. It is spread by inhaling virus-laden dander. It is poultry-specific, meaning it cannot transfer to mammals, including humans. Marek’s disease can be serious and have a 1-50% death rate in a flock, depending on the breed of the birds.

For a conventional farmer (even a conventional organic farmer), it’s a smart choice to vaccinate.

Marek’s disease is a big deal when chickens are raised by the thousands in confined and unsanitary conditions, which is the unfortunate fate of most chickens in the US. And, given that most modern farmers struggle to make a living, they absolutely cannot afford a loss.

And get this >>> Biologics and vaccines are 100% allowed and encouraged for USDA organic farming. 

There are 7 common vaccines given to chickens: Marek’s Disease, Mycoplasma gallisepticum infections, Infectious Bursal Disease, Encephalomyelitis, Fowlpox, Laryngotracheitis, and Newcastle disease/Infectious Bronchitis.

It gets worse. The Marek’s vaccine makes the virus more dangerous.

The vaccine for Marek’s disease is a “leaky” vaccine. This means that it prevents dangerous symptoms in vaccinated chickens, but doesn’t stop the virus from replicating and spreading to other chickens. This is different from a “perfect” vaccine that prevents symptoms and transmission for life.

“Leaky” vaccines allow the virus to live, mutate, and sometimes become stronger. This can create what’s known as “hot” strains or “superbugs”. They spread and kill the host more quickly.

There have been studies done where unvaccinated chickens are introduced to chickens vaccinated for Marek’s disease. The result? All the unvaccinated chickens died. 

Now, what if the Marek’s vaccine stops working for the mutated virus? Or what if the virus mutates to transfer to humans? These are apocalyptic thoughts that are sadly all too real in the current world.

There is light. There is a BETTER and MORE EFFECTIVE way to prevent disease in chickens. 

When birds are treated humanely, raised in small flocks, given space and plenty of fresh air, and fed a healthy soy-free diet… well, there’s not much to worry about. You will most likely have naturally healthy birds.

Miller’s chicks never have and never will be vaccinated!

We raise chickens to be naturally healthy. And, in the 10+ years of doing it, we’ve never had a problem with disease. 

In fact, the only problem Miller’s has ever had with disease was caused by a vaccine. In 2018, one of our cows was discovered to be spreading RB51 in milk. RB51 is the strain of brucellosis found only in the brucellosis vaccine. The farmer had purchased the cow 6 years prior without knowing it had been vaccinated. 6 years later, with no symptoms, the cow was still harboring RB51. You can read more about that issue and how it was resolved here.

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*Update 1/28/26: Time has passed, and Miller's has had one more issue with disease: Campylobacter was found in the milk. You can read the story of what happened and how it was resolved here.