Most backyard chickens need only one vaccine: Marek’s disease, given at hatch. Beyond that, the vaccines your flock needs depend on whether your birds are exposed to outside poultry, whether disease is present in your area, and whether you run an open flock that regularly brings in new birds.
Marek’s Disease: The One Vaccine Every Chicken Should Get
Marek’s disease is caused by a virus found in virtually every flock. It spreads through feather dander, meaning your chickens don’t need direct contact with sick birds to catch it. The disease attacks the nervous system and immune system, causing paralysis, tumors, and death, primarily in birds between 2 and 7 months old. There is no treatment.
The vaccine must be given at hatch, ideally on day one of life, before chicks encounter the virus in their environment. If you’re ordering chicks from a hatchery, you can request Marek’s vaccination for a small added fee (often less than 25 cents per chick). If you’re hatching your own eggs, you can purchase the vaccine and administer it yourself, though the vaccine comes in large-dose vials designed for commercial operations, which can be wasteful for small batches.
Marek’s vaccine does not prevent infection. Vaccinated birds can still carry and shed the virus. What it does is prevent the tumors and paralysis that kill unvaccinated chickens. Because the virus is essentially everywhere, skipping this vaccine is the single riskiest decision a flock owner can make.
Newcastle Disease and Infectious Bronchitis
These two respiratory diseases are the next tier of concern. Newcastle disease causes respiratory distress, nervous system symptoms, and drops in egg production. Infectious bronchitis targets the respiratory tract and can permanently damage the reproductive system in young pullets, reducing their egg-laying ability for life.
Vaccination against Newcastle disease is recommended in certain geographic areas and for birds that attend shows or exhibitions. Infectious bronchitis vaccine is similarly situation-dependent. In commercial operations, both are given as a combination vaccine through drinking water or spray, starting at 2 to 3 weeks of age with boosters every 60 to 90 days. For backyard flocks, the simplest route is to buy chicks that were already vaccinated at the hatchery, since these vaccines can be difficult to source in small quantities.
If your birds never leave your property, you don’t bring in new birds, and these diseases aren’t circulating in your region, vaccination may not be necessary. But if you have an open flock or live in an area with active outbreaks, both vaccines are worth pursuing.
Fowl Pox
Fowl pox spreads through mosquito bites and direct contact, causing wartlike lesions on the comb, wattles, and face (the “dry” form) or plaques inside the mouth and throat (the “wet” form, which can be fatal). The disease is more common in warm, humid climates where mosquito pressure is high.
The vaccine is given using a wing-web applicator, a two-pronged tool that’s dipped in vaccine and then poked through the thin skin of the wing web. A small scab or “take” forms at the site within a week, confirming the vaccine worked. This is a vaccine you can administer yourself, and it’s worth considering if fowl pox has been seen in your area or if mosquitoes are a persistent problem on your property.
Infectious Laryngotracheitis
Infectious laryngotracheitis (ILT) causes severe respiratory distress. Birds gasp for air, stretch their necks, and may cough up blood. Mortality can be significant in unvaccinated flocks. ILT vaccines are live vaccines typically used in two situations: as an emergency response during an active outbreak, or as a routine measure in areas where the disease is endemic.
This is not a vaccine to give “just in case.” Live ILT vaccines can establish carrier birds that shed the virus, potentially introducing the disease to a flock that never had it. Only vaccinate if ILT is a confirmed problem in your region.
Coccidiosis: Vaccine or Medicated Feed
Coccidiosis isn’t caused by a virus or bacterium. It’s a parasitic infection of the intestinal lining that causes bloody droppings, weight loss, and death in young chicks. You have two options for prevention, but you should only use one at a time.
The first option is a coccidiosis vaccine, which many hatcheries offer alongside the Marek’s vaccine. It exposes chicks to small, controlled doses of coccidia so they build natural immunity. The second option is medicated starter feed containing amprolium, which blocks the parasite’s ability to absorb a key nutrient. Amprolium is not an antibiotic. You feed it for the first six weeks, then gradually transition to non-medicated feed over about 10 days, allowing the birds to develop their own immunity during the changeover.
The critical rule: do not feed medicated feed to chicks that received the coccidiosis vaccine. The amprolium will interfere with the vaccine by killing the controlled dose of coccidia before the chick’s immune system can learn to fight it. When you order vaccinated chicks, confirm whether coccidiosis vaccination was included so you know which type of starter feed to buy.
Avian Influenza
As of 2025, the USDA has conditionally approved a poultry vaccine for avian influenza, but it is not yet part of standard vaccination programs for backyard flocks. The federal government has allocated up to $100 million for vaccine research and development, with the goal of reducing the need to depopulate entire flocks during outbreaks. Whether avian flu vaccination becomes routine for small flock owners will depend on regulatory decisions and how the disease situation evolves.
How to Decide What Your Flock Needs
The general principle is straightforward: don’t vaccinate against diseases that aren’t present in your area. Unnecessary vaccination adds cost and stress to your birds without benefit. Here’s a practical framework for deciding:
- All flocks: Marek’s disease vaccine at hatch. This is non-negotiable given how widespread the virus is.
- Flocks that attend shows or swap meets: Newcastle disease and infectious bronchitis, since your birds will encounter poultry from many different sources.
- Open flocks (new birds added regularly): Newcastle disease and infectious bronchitis, plus consider fowl pox if you’re in a mosquito-heavy area.
- Flocks in endemic areas: Whatever diseases are circulating locally. Your state poultry extension office or local veterinarian can tell you what’s active in your region.
- Closed flocks with no disease history: Marek’s at hatch may be the only vaccine you need.
Practical Tips for Vaccine Handling
Most poultry vaccines are live, meaning they contain weakened versions of the actual pathogen. They require refrigeration between 35°F and 46°F and must never freeze. Once you reconstitute a freeze-dried vaccine (mixing the dried cake with the diluent), it begins losing potency quickly. Use it within the timeframe on the label, typically one to two hours.
Poultry vaccines are sold in large-dose vials, often 1,000 or 5,000 doses, because they’re designed for commercial operations. For a small flock of 6 to 12 birds, you’ll use a tiny fraction and discard the rest. This is one reason many backyard flock owners find it more practical to order pre-vaccinated chicks from a hatchery rather than buying and administering vaccines themselves. The cost of hatchery vaccination is typically a few cents per bird, far less than purchasing a full vial.