For the small flock owner, vaccination is generally necessary only if the birds have had disease problems in the past, may possibly be exposed to other birds (eg, at poultry shows, meat swaps, or wild bird access), or if new birds are introduced to the flock (open flock). Birds should not be vaccinated for a disease not present in their local area, because this will only introduce new organisms into the flock. Also, a sick bird’s immune system is compromised and unable to withstand the stress of vaccination.
If certain diseases are a problem in a backyard flock, vaccination may be recommended after veterinary consultation. Marek disease is present in almost every flock, and vaccination of chickens is strongly recommended in all cases; vaccination is key for control and is inexpensive. Backyard poultry owners may purchase chicks from hatcheries and request their chicks be vaccinated at hatch with serotype 3, or they can vaccinate their own chicks if hatched onsite. Because the virus is ubiquitous and spreads through feather dander, vaccinating birds at hatch before they are most susceptible (2–7 months) is critical to establish early immunity. There are three serotypes of Marek disease: 1, 2, and 3. Because most backyard chickens are vaccinated only for serotype 3, they may not be fully protected. In addition, vaccination does not prevent infection or shedding of the field virus.
Newcastle disease virus vaccination may be recommended in certain geographic areas and in birds that frequent shows and exhibitions. However, commercial vaccines are only sold at large quantities in lots of 10,000 dose vials, which presents a challenge for small flock owners that only require small amounts (eg, less than 100). In addition, some live vaccines are only approved for administration by approval of the state veterinarian, and regulations differ by state. If certain vaccines (eg, infectious bronchitis virus, infectious bursal disease, etc) that might be a challenge for accessibility are desired for specific needs, it may be best to tailor those needs and receive vaccinated chicks directly from the hatchery.