Immunization through vaccination is a commonly used

method of reducing the risk (increased ID50) and consequence

(reduced pathogenicity) of bird or flock exposure to a disease-causing agent..

Vaccination is the practice of administering live and/or killed vaccines which have been modified to minimize

disease manifestation yet maximize immunity.

the primary purpose of immunization is to raise

the ID50 of the flock to prevent clinical disease following

subsequent challenge.

While some vaccines are given to protect

that individual bird against disease,

others are given to pass the

protection on to the next

generation, and others are given to prevent disease in the hen

and subsequent transmission of the disease to the chick

Vaccines and vaccine programs vary widely in their

effectiveness, and this is frequently by design. Some vaccines

are designed to incite high levels of immunity to protect birds

in the face of aggressive endemic disease challenges, such as

vvND.

These vaccines may cause a mild form of the

disease themselves but are deemed appropriate and

useful because of the risk associated with eventual infection of the

deadly field pathogen.

Vaccine selection and how they are programmed

frequently becomes an exercise in risk management and cost

efficiency.

Local conditions must always be

considered when evaluating and critiquing a

vaccination program.

A second reason for the vaccination

of poultry flocks is to hyper immunize hens to maximize

maternally derived antibody passed through the egg to the

hatching progeny.

Chicks frequently receive up to 3 weeks of protection from maternal anti-

bodies, allowing their immune system to mature to a level capable

of eliciting an efficient active immune response if exposed to a

potentially harmful virus or bacteria.

Antibodies are not always completely protective but for

viruses such as infectious bursal disease (IBD), many areas of the

world have found maternal antibodies a very useful tool in IBD

prevention and control.

The success of vaccination does not rest solely with the manufacturing or research of

vaccines. More important is the maintenance of the cold chain, protection of

the vaccine from the elements, and the correct application of the vaccine to the

bird.

vaccination programs should be documented

for each operation by the responsible veterinarian and

operations manager. All vaccines must be stored at the

correct temperature. Most vaccines require

refrigeration at 2°C to 8°C

Some vaccines, mostly killed oil

vaccines, can be safely stored at

room temperature. Some vaccines

need to be stored at temperatures

below 0°C..

Vaccines are adversely affected by

exposure to sunlight and heat. Vaccines must be administered

using suitably cleaned equipment and be given to every bird in

the defined epidemiological unit

Live vaccines are widely used throughout

the world because they are commonly effective when mass

applied, and they are relatively economical.

immunity from live vaccines is generally

short-lived, particularly following initial

exposure. Some exceptions to this exist for

vaccines such as for infectious laryngo-

tracheitis, fowl pox, and Marek’s disease,

which give long-lived immunity.

Inactivated vaccines or killed vaccines used in poultry are

generally whole bacteria or virus preparations combined with

an adjuvant that are designed for subcutaneous or intramuscular

injection

They are frequently, but not always, used in

commercial egg layer and breeding birds to

stimulate long lasting immunity and/or antibody levels to specific antigens.