Should you vaccinate your chickens? Well, yes and no. There are several vaccines available, and you should do your research before you buy. For example, you can give the coccidiosis vaccine to young chicks. But if you do, never feed medicated chick feed or you will nullify the vaccine. Some vaccines need to be administered once, some on a regular rotation through life. Some will cause your chicken to test positive for the disease, since the vaccine is a live variant. Some are affordable, some prohibitively expensive. But none are as controversial as the Marek's vaccine. (Just FYI - directions for administering the vaccine are at the bottom).

The Marek's vaccine is the only vaccine used here at Green Grables. Marek's is essentially a virus that causes cancer in chickens - there are a few varieties, but all involve a cancer or a cancer-like result. It most often shows up in chickens that are aged 6 weeks up to 2 years, but can appear at any time in a chicken's life. One sign of Marek's in young chicks can be coccidiosis , especially coccidiosis that occurs multiple times. Marek's doesn't cause coccidiosis, but the virus lowers the chick's ability to fight off cocci. You may not know your chicken died of Marek's since it can affect so many aspect of chicken health. They can have tumors anywhere in the body, so they may just waste away, or they may look perfectly healthy and then keel over dead. They could have symptoms that look like respiratory disease with lung tumors, or they may die of something like respiratory disease because Marek's affects the immune system, making the chickens more prone to infection. "Cool" varieties can cause issue in just a few birds, or simply have a low death rate. "Hot" varieties can rip through your flock, killing every bird. If a bird is exposed to any variety and survives, it then carries the virus for life, much like the chicken pox virus in humans. During times of stress, the virus can activate, causing the bird to shed virus and infect more birds. If you have had a confirmed case of Marek's on your farm, you must consider every bird a carrier. And the Marek's vaccine has a problem. It's a "leaky" vaccine, meaning that properly vaccinated birds can still catch and shed the virus. The vaccine just prevents the virus from causing tumors in most birds.

So what to do? There are two main schools of thought - vaccinate every bird upon hatch, or don't vaccinate anything and attempt to build up an immunity. So first, vaccinating - birds need to be vaccinated before they are exposed to the virus. Then they need a while without exposure to let their body build up the immunity in response to the vaccine (minimum 4 days, but we prefer a minimum of 2 weeks). Unfortunately the virus can travel via bird dander through the air. So I vaccinate as the chicks come out of the incubator. Then they stay in my pottery studio for 3-4 weeks. No one is allowed in without a shower and fresh clothing, and the room has a good air filter. Vaccinating is not super simple at times. Maybe I could get away with a more relaxed routine, but Marek's is extremely common in NC, and d'Uccles can be very susceptible to it. I've put a lot of money and time into my flocks, and with overnight shipping, the vaccine is not inexpensive, so I'd rather err on the side of caution. As an aside, should you vaccinate older birds? It's won't hurt them, but most likely they've already been exposed, so it probably won't help them either. When I first bought show birds, a month before I brought them home I did vaccinate every bird in the flock that had not had a vaccination. I was aware that the chances of exposure increase with showing, so it was worth the cost to me, even though I knew that it would most likely not affect anything with older birds.

Can you build up resistance to Marek's in your flock? Perhaps. Certain breeds are definitely more susceptible (leghorns, Belgian breeds, silkies, sebrights, etc.), as are certain lines in certain breeds. You can skip the vaccine, and you may lose a bird here and there... and you may think "Yay! I have a great flock that is not affected by Marek's!" But what if your flock has only been exposed to "cool" strains? You simply do not know whether you have an immune flock or whether you've just been lucky. And someday a wild bird may fly over or nest in your yard, shedding a "hot" strain in it's feather dander and poop. And that variety may kill your whole flock. It's not a pretty scenario. And what if you take birds to a show? According to all accredited poultry units in the US, all of those birds have been exposed to some form of Marek's. The general consensus in agricultural colleges with poultry divisions is that if you have chickens outside, you have some form of Marek's. So you may get lucky and have a group of birds that was either vaccinated or just not very susceptible to the majority of Marek's strains in your area. You may never see an issue, or you may lose birds here and there to Marek's and not even know it, since it mimics so many other issues.

You can read up on Marek's if you want more details. I will put some links at the end. There's lots of scary information, but keep this in mind: Marek's is everywhere, and your chickens will be exposed whether you know it or not. This happens to all chicken owners. The web will make you think you have no choice but to put down your flock and start over. I've never had a chicken test positive for Marek's at Green Grables, but I've done a lot of research, so I know it's quite possible and probable that there is a strain here. We've had some necropsies at the state lab. Nothing yet has pointed to Marek's, but that really doesn't prove anything. I'm trying to be very open and realistic here, because it's hard to find anything but doom and gloom about this on the web, which seems wrong when this is such a prevalent issue in the chicken world. I've talked with big farmers, little farmers, agricultural professors, and show people. And I've learned that a lot of these people take a mixed approach. Vaccinating is often used, especially with susceptible or rare breeds. And if a chicken shows any signs of a serious nature (paralyzed, wry neck, swollen eyes, etc), the chicken is put down. That's a hard hard fact when you have a small flock with just a few pets. I've also spoken to people who have invested in vets and chicken wheelchairs. I can't say that any people are wrong in what they do. With pets, it is harder to put them down for sure... but that means there are more chickens who are sick and shedding more severe forms of the virus, which can be transmitted on the clothing and shoes of the owner. So Marek's is around to stay. 

You make your choice and I will make mine. Shame and guilt need to be put aside. This is personal choice, based on breed susceptibility, risk tolerance, and specific situations. No one answer is right for everyone. Vaccination will not endanger the birds of others, and vaccinated birds are protected from disease should an unvaccinated bird expose them.

I wish that conversations on this issue were more open - because what do we do? Let responsible farmers follow the most common guidelines on the web, culling or closing their flocks, while those who are less trustworthy continue breeding and selling to the unknowing customer? Do we let rare breeds die out if they are in an exposed flock? Or do we concentrate on education? Showing others how to vaccinate, which lines and breeds are more susceptible, discussing how to best care for flocks in order to best support their immune health? Maybe more discussions on how to ensure parental health, which greatly affects the health of their offspring? I don't know the answers to all of this, but these discussions need to be had openly in the chicken world. 

Until that happens, I will be as open with my customers as I can. I vaccinate my chicks as they come out of the incubator, and keep them as safe as possible for a few weeks so their immune systems can come online. There have been no documented accounts where vaccinated chicks spread Marek's to unvaccinated chicks. The directions for the vaccine do state that chicks should be kept separate from other chickens for two weeks, but that is so the vaccinated chicks are not exposed, not because they could spread the vaccine virus. It is a live virus vaccine, but the virus used is a turkey virus that does not affect chickens. A recent study hints that unvaccinated chicks may get some sort of low protection by being with vaccinated chicks, but that's it so far. Another myth - keeping turkeys with chickens does not result in immune chickens. That's not how the immune system works. A couple of years ago I vaccinated chicks in batches to save money, not understanding that each day unvaccinated is a day they could be exposed. Now I split my vaccine in order to save a bit of money, but each chick is vaccinated on day one. And I hatch a lot. 

So, here we go! Vaccinating... I get my vaccine from or Twin City Poultry Supplies. I get several bottles since I hatch a lot, so I just check prices. The vaccine must be overnighted, which is expensive, but if it gets warm, it it no longer able to be used. Improper storage can result in improperly vaccinated chicks. I keep mine in the fridge. You get two bottles. A large bottle of diluent (or a bag, depending on where you get it) and a tiny bottle with a wafer at the bottom. Directions tell you to add all of the wafer to all of the diluent (liquid) and use it within one hour. There are 1000 doses and they are no good after that time period. You must keep it cool and swirl to mix regularly during vaccination. I use a 22 gauge needle. You can use a 1ml syringe (you give 0.2ml/chick) or I use a vaccine gun, which makes things much more simple with larger numbers of chicks. 

I split my vaccine to make it more affordable. You can split it up any way you like - I choose to split my wafer into four sections, using a tiny chemistry spatula. One issue - the wafer absorbs water from the air, which will ruin it. So you need to keep that bottle closed as much as possible. You need to split the wafer in a dry, non-humid place very very quickly, get that lid back on, and get it back into the fridge. I also use 1/5 of the liquid for 1/4 of the wafer. This ensures that the vaccine is at a high enough concentration, even if my 1/4 wafer is not exactly 1/4 of the wafer. Initially, I split the wafer using a scientific scale, but that results in the wafer being out too long. If it gets sticky, it's best not to use it. 

So remember:

1. Keep the wafer cold and dry. Open the jar infrequently and swiftly. Get it back into the fridge.

2. If you split the wafer, do it simply to keep it quick. Compensate for splitting error by decreasing the liquid (1/4 wafer into 50ml liquid). 

3. Vaccinate within the hour, keeping the vaccine cool and swirling between each chick to keep it well mixed.

4. Make sure you see a little bubble under the chick's skin - otherwise it is not vaccinated. I use a bit of water to wet down the fluff so I can see (I used alcohol initially, but the cold from the quick evaporation was hard on them, as were the fumes).

5. Dispose of unused vaccine. I add some rubbing alcohol to inactivate the vaccine.

6. I vaccinate weekly during hatching season, so this part is easier for me, but I vaccinate a second time at two weeks.

Here are some videos for you if you'd like a visual.

Supplies for vaccinating

Diluting the vaccine

Assembling the vaccine gun

Setting up the vaccine gun

Note: I usually hatch every week in the hatching season, so my chicks receive a second vaccination at 2 weeks. Easy for me to do, since I'm vaccinating every week. Some studies have shown increased protection with the second vaccine.

Here are some information links:

Marek's disease (backyard chickens)

Marek's disease Penn State Extension

Product directions for Marek's vaccine

Marek's vaccine at Jeffers Pet

Vaccine gun at Jeffers Pet

Needles and syringes at Jeffers Pet (I use 22gauge needles and you'd need 1cc syringes for vaccinating. I use a 60 ml syringe with an 18 gauge needle to get out the 50ml diluent)

100ml glass bottle for vaccine gun (I typically take off the metal at the top and just reuse these over and over. I clean them with hot water and soap, then rubbing alcohol.


  1. I have read that vaccinating them 14 to 21 days after the first dose can also help boost a better response to the vaccine.