Infectious bronchitis is a common highly contagious disease that affects all ages of chickens.

Clinical signs are snicking, diarrhoea and damage to the reproductive tract resulting in a decline and poor egg quality. The effects depend on the strain and virulence of the virus, the age of the chicken, maternal antibody, complicating infections and environmental stress factors.

Infectious bronchitis requires multiple vaccinations.  The first vaccinations are with the live vaccines. This live vaccination programme provides cell-mediated, local mucosal immunity to the reproductive and respiratory system of the layer and breeder chickens.  The final vaccination is the killed Inacti/Vac IB1 vaccine, which is given by the subcutaneous route at least 4 weeks after the final live virus vaccine when the chicken is 16 - 20 weeks of age.  This vaccine provides long-lived systemic protection for the chicken against infectious bronchitis.  It is essential for all vaccinations to be given for protection of the layer and breeder chickens throughout the lay.  Some layer farmers choose to vaccinate chickens with the live vaccine at 8 - 10 week intervals throughout the laying cycle administered by drinking water or spray.