In order to exploit the potential of the inactivated vaccine the chickens must be properly primed with live vaccines. Highest titres will be obtained when an interval of at least 4-6 weeks is left between the last live vaccine and the inactivated vaccine.
Vaccination programs may be simplified by combining inactivated antigens against two or more serotypes or two or more diseases into one vaccine.
The following graph illustrates the serological response in layer chickens as measured in the HI test after administering a vaccination program that includes live and inactivated vaccines in comparison to a program based only on live vaccines. Notice that a consistent titre level is only obtained after the use of the inactivated vaccine.
Production of HI titres against Infectious Bronchitis virus (Massachusetts) in layers