The effect of the plant-derived preparation (Tilia cordata Mill., Thymus kotschyanus Boiss and Hohen., Matricaria chamomilla L.) Imuneo on the immunity indices in chickens vaccinated against avian infectious bronchitis was studied, and the immunostimulatory efficacy was evaluated. In the group of chickens treated with immunostimulants, a significant increase in their immune status was recorded. The immunostimulating effect of Imuneon was determined. Microbicidal and immunostimulating properties of plant-derived Hedalin preparation were studied. The expediency of using immunostimulating drugs in poultry complexes is presented.