1. Develop your own vaccination program; do not blindly copy someone else’s existing program. Based on factors such as disease incidence in the poultry industry in your area, the purpose for which the chickens are raised, and the types and epidemiological characteristics of common diseases, develop a practical vaccination program under the guidance of local livestock personnel. If you raise commercial laying hens, do not vaccinate against avian encephalomyelitis. In areas free of infectious laryngotracheitis, vaccination against infectious laryngotracheitis is not recommended. Avoid vaccinating flocks that are at the peak of egg production whenever possible.
2. To strengthen the immune response, repeat vaccination is necessary. For example, Newcastle disease vaccination can be given 3–5 times. Provided the vaccine is reliable, use vaccines from the same manufacturer for both the initial and repeat vaccinations whenever possible to achieve more lasting immunity.
3. Do not excessively increase the vaccine dose. In general, when vaccinating by intranasal administration, eye drops, wing-web stab or injection, simply follow the manufacturer’s instructions. For vaccination via drinking water, the dose may be increased by 1.5–2 doses per chicken. For emergency vaccination with Newcastle disease vaccine, strain IV, the usual dose is 4–6 doses per chicken.
4. For vaccination via drinking water, withhold water for 2–3 hours before administering the vaccine, and for 1–2 hours afterward. Water is often not withheld after vaccination, resulting in poor immune responses. Water must be withheld both before and after vaccination to achieve a satisfactory immune response.
5. Give inactivated oil-emulsion vaccines and freeze-dried live attenuated vaccines equal importance, and use them in combination. Inactivated oil-emulsion vaccines are easy to store and transport, have a standardized dose, and provide a long immunity period; however, they are expensive and inconvenient to use. Extensive clinical practice has shown that using inactivated oil-emulsion vaccines alone does not produce a fully satisfactory immune response. For Newcastle disease prevention and control, use both inactivated oil-emulsion vaccines and live attenuated vaccines to achieve the best results.
6. Do not administer live attenuated vaccines at the same time as injections of hyperimmune serum or egg-yolk antibodies. Live attenuated vaccines are antigens, whereas hyperimmune serum and egg-yolk antibodies are antibodies. Using them at the same time causes a neutralization reaction and greatly reduces the immune response. If both are to be used, leave an interval of at least 2 weeks.
7. Do not add antimicrobial drugs to vaccine diluent. Experiments have shown that most antimicrobial drugs can alter the osmotic pressure or pH of the diluent, reducing the survival rate of viruses in the vaccine and thereby weakening the immune response.
8. Subcutaneous or intramuscular injection cannot be used as a substitute for wing-web puncture vaccination. Experiments have shown that existing fowlpox vaccines are suitable only for administration by the puncture method or the feather-follicle application method.
9. Do not divide large-dose vaccine into smaller portions. After the original lyophilized vaccine has been frozen and thawed, the virus potency decreases. In addition, bacteria may be introduced during repackaging, and humidity may differ before and after repackaging; all of these factors can affect vaccine quality.