This study comprises the immune response of pregnant mares and their foals to monovalent inactivated freeze-dried equine influenza (El) vaccine, reconstituted in diethylaminoethyle (DEAE) Dextran solution as an adjuvant. It was found that mares developed high haemagglutinating inhibition (HI) titre at 3 weeks post vaccination and remain with protective level up to 6 months, while their foals had moderate (HI) antibodies within  48 hours post colostral suckling, the HI antibodies rise to a level similar to their dams within one to two weeks then persisted with considerable level up to 6 months of their age.