Observation on flock immunity to Newcastle disease after routine vaccination and experimental aerosol vaccination.

Serological responses in groups of chicks either routinely or experimentally vaccinated with Newcastle disease vaccines via various routes were compared by the micro method of HI test. The lowest serological response to vaccination was found in those groups which had been routinely vaccinated with LaSota strain in drinking water, but a better response was observed in the farm with improved environmental conditions and lower maternal antibody level. Antibody titers in experimentally vaccinated groups were higher than those of routinely vaccinated groups, and the highest antibody response was obtained by aerosol vaccination.