Lay summary
Preschool wheeze is a common cause of hospital admission of preschool-aged children worldwide and the most common cause in Australia and New Zealand. Current prevention strategies are ineffective and potentially harmful. Novel approaches are needed. OM-85 is an orally administered bacterial lysate that stimulates immune responses against viral infections and reduces the excessive inflammation of the respiratory mucosa associated with wheezing episodes. In placebo-controlled trials, OM-85 reduces recurrent respiratory infections in children. Larger studies are required to evaluate whether OM-85 prevents wheeze-related hospitalisations. Children 1-5 years old with a history of wheeze and admitted to participating Australasian hospitals (seven in New Zealand) with a wheezy illness will be eligible. 2268 children will be enrolled and randomly assigned 1:1 to OM-85 or placebo. This trial will determine the efficacy of OM-85 for preventing hospitalisations in preschool-aged children with recurrent wheeze and assess the effect of OM-85 on subsequent recurrent wheeze events.