Vaccination with live IBDV vaccines
Live vaccines are administered to achieve active immunity. Interference of MDA is the crucial problem in determining a successful live IBDV vaccination schedule.
- Vaccinating in the presence of high levels of MDA results in vaccine virus neutralisation and no immunity.
- Waiting until an age when MDA levels have declined to very low levels could result in a pathogenic field virus challenge before vaccination. (See this figure).
- To assist in determining the optimal vaccination age a formula (Deventer Calculator) based on the MDA titre of young chicks has been developed.
Interference of MDA is the crucial problem in determining a successful live IBDV vaccination schedule.