For active immunisation of weaned pigs from three weeks of age to reduce intestinal lesions caused by Lawsonia intracellularis infection and to reduce growth variability and impairment of weight gain associated with the disease. Under field conditions, the improvement in average daily weight gain (ADG) was seen to be up to 30g/day when vaccinated pigs were compared to non-vaccinates. Onset of protection occurs as early as three weeks post vaccination and lasts for at least 17 weeks.