Mareks vaccine is recommended for the vaccination of healthy one-day-old chicks only, to aid in the prevention of the signs and lesions of Mareks disease. Give subcutaneously only (injected into the bird). For vaccination, an automatic syringe with 22- to 20-gauge needles, 3/8-inch to 1/2-inch in length, is recommended. Make certain that all equipment is sterilized and change needles frequently. Inject each chick subcutaneously with 0.2 mL (two-tenths of a milliliter) of the vaccine. Inject into the back of the chicks neck by pinching the skin.