The effectiveness of Infectious Laryngotracheitis Virus Recombinant Vaccines depend on the age of the embryo at vaccination and proper vaccine delivery, according to a study funded by the U.S. Poultry & Egg Association.

Research was conducted to determine the degree and onset of protection induced by ILTV when applied in ovo and subcutaneously; to determine if shedders are produced in recombinant vaccinated chickens; and to improve detection of antibodies produced following vaccination.


Embryo vaccination at 18-19 days is the optimal age for vaccination, according to the study, and optimal efficiency of recombinant vaccines strongly relies on proper vaccine delivery — namely, precision and consistency of equipment utilized. Compared to traditional vaccines, ILTV provided partial protection against laryngotracheitis, but did not stop replication of the challenge virus in the upper respiratory tract.