Respiratory Diseases: Vaccination and Immune Response

Newcastle Disease Virus, Infectious bronchitis virus (IBV), Avian metapneumovirus and other respiratory agents are, in spite of vaccination(s), major causes of respiratory problems in broilers and of poor egg production in breeders and layers in many parts of the world. Many vaccines that are being used have shown under experimental conditions that they are able to provide a high level of protection against an homologous challenge. This raises the question: why do we have outbreaks in vaccinated flocks? 

Possible reasons of (partial) failure of the protection induced by vaccination(s) are for example heterologous challenges, immunosuppression, very short or long intervals between vaccination and challenge, interference by co-infections, interference by maternally derived antibodies and last but not least, inadequate application of the vaccine or vaccines.

This presentation discusses factors that can influence the efficacy of the vaccination and the immune response to the vaccination