To evaluate the efficacy of combined live and inactivated vaccination program, a group of 28 commercial pullets were vaccinated with live Salmonella vaccine (two administrations at 1st and 6th weeks of age) via drinking water and revaccinated with inactivated Salmonella vaccine (at 16th weeks of age) by intramuscular route. They were evaluated in comparison to another group of 28 birds vaccinated with a live vaccination program (three administrations at 1st, 6th and 16th weeks of age) via drinking water.
Ruffled feathers, paralysis and incoordination, and, lastly, the death of the bird were the clinical signs recorded. Once birds were early infected at 24 days of age, the birds in the different groups were observed until 34 days of age. Over the course of these days, clinical signs were only observed from 30 days of age on in Group A (control group).