An immunity capable of resisting challenge to infection is normally produced in 7 to 10 days following vaccination of susceptible chicks, and lasts for approximately 3 to 4 months. Where necessary revaccination at 3 to 4 month intervals is advisable.

Suggested vaccination programmes are available on request.

In any animal population there will be a small number of individuals which fail to respond to vaccination. Successful vaccination depends upon correct storage and administration of vaccine and the bird’s ability to respond. Immune competence can be influenced by genetic factors, intercurrent infection, age, nutritional status, concurrent drug therapy, stress, etc.

Maternally-derived antibody (MDA) can interfere with the development of active immunity. Where it is likely that recent field infection or vaccination of the parent flock has stimulated a high antibody titre and consequently a high level of MDA, the timing of the vaccination programme should be planned accordingly.