The study was conducted on 500 commercial broiler chickens fed on diets supplemented with Brewer`s yeast, (Saccharomyces Cerevisiae) in inactive cells. The Brewer's yeast has a high nutritional value in addition to containing a high level of Nucleotides. There are no negative effects when it is used in a limited rates. It is a natural substance and it doesn't leave any residues in meat or eggs. The inactive Yeast was used in the form of powder which was mixed with the feed used during the feed manufacturing process and according to the specified dose, 1000 g yeast per ton feed. In order to compare the impact of this yeast on the specific  and non- specific immunity of infectious bursal disease (IBD) The titre of three types of commercial vaccines used in Syria against infectious bursal disease was estimated. The vaccines are two imported (1,2) and a local one (3). The study has confirmed that there were clear significant variances (P<0.05) between the control and the experimental groups which added to its feed a yeast beer during all stages of breeding for the percentage of lymphocytes which were higher in treated groups than in the control ones.