The immunological reactivity of the organism at stimulation of various antigens is influenced by many factors, among which an important role have parasite infection. The last ones have an opportune character, when the parasite agent proliferates on primary or secondary immunodeficiency fond. The parasite antigens provoke a nonspecific stimulation of B lymphocytes and their over demand disturbs the humoral immune response toward the antigens of infection origin. The aim of this study is to investigate the impact of the poliparasitism and antiparasitic chemotherapy in prophylaxis of postvaccinal immunodeficiencies of parasitic order. The study was accomplished on 4 groups of 5 calves (4-6 months) of Holstein race. The group I (negative control) was constituted of noninfected and vaccinated with anticolibacillar vaccine bovine. The vaccine was obtained from autochthon stem of E.colli antigens. The vaccine was administrated subcutaneously in two rounds with an interval of 14 days between them. The first vaccine dose was of 7,5 ml and the second one 10 ml. Lot II (positive control) – bovine infected by Strongyloides papillosus, Neoascaris vitulorum, Eimeria bovis, E. smithi, E. zuernii, E. ellipsoidalis, untreated and vaccinated similar to lot I. Lots I and II served as control groups. Lot III – bovine infected by S. papillosus, N. vitulorum, E. bovis, E. smithi, E. zuernii, E. ellipsoidalis and complexly treated against parasites with Amprolium, Albendazolum 2,5% and Tylosinum 200, and then they were immunized with anticolibacillar vaccine similarly to group I. Lot IV – bovine infected by S. papillosus, N. vitulorum, E. bovis, E. smithi, E. zuernii, E. ellipsoidalis and complexly treated with Levamisolum, Amprolium, Albendazolum 2,5% and Tylosinum 200. The Levamisolum was administrated as an immunomodulatory drug. At the end of the treatment the calves were immunized with anticolibacillar vaccine. The results of the parasitological laboratory investigations revealed an invasion extensity by S. papillosus of 56% and an invasion intensity (II) – 2-16 larvae, Neoascaris vitulorum – 59% and II – 5-8 eggs, Eimeria sp. – 65% and II – 2-14 oocysts. Immunological research results show that, after 15 post therapeutic days, in the group (IV) of infected animals (S. papillosus, N. vitulorum, E. bovis, E. zuernii, E. ellipsoidalis), treated antiparasitic (Levamisolum, Amprolium, Albendazolum 2,5%, Tyilosinum 200) and immunized with anticolibacilar vaccine, it was found an average level of 1783.5 Ѓ} 256.4 antibodies, i.e. higher by 99.6% (P<0.001) than the initial level; by 80.4% (P <0.001) compared to group (III), infested and treated similarly, but without immunomodulatory (Levamisolum); by 80.0% (P<0.001) compared to group II (positive control), infected and untreated, but only by 29.0% (P<0.001) compared to group I (negative control). Therefore, the obtained results justify the use of Levamisolum in the antiparasitic treatment schemes, which is why it is recommended as a remedy for prophylaxis of parasitic postvaccinal immunodeficiencies. The work was performed within the fundamental project 15.817.02.12F at the Institute of Zoology of A.S.M., financed by the Supreme Council for Science and Technological Development of A.S.M.