Assessing the Reduction of Recurrent Admissions Using OM-85 for the Treatment of Preschool Wheeze (ARROW): protocol for a multi-centre, randomised, double-blind, placebo-controlled trial

Aims: Acute wheezing illnesses are among the most common reasons preschool-aged children are admitted to hospital. Readmission rates are high, and novel preventive strategies are required. OM-85 is an orally administered bacterial lysate that stimulates anti-viral immune responses and reduces excessive airway inflammation associated with wheezing episodes. The aim of the Assessing the Reduction of Recurrent admissions using OM-85 for the treatment of preschool Wheeze (ARROW) trial is to determine the efficacy of OM-85 in preventing hospital readmissions in children admitted to hospital with preschool wheeze. The primary outcome is hospital admission due to an acute wheezing illness during the 12-month treatment period. Secondary outcomes include the frequency and duration of wheeze episodes and the cost-effectiveness of the intervention. Methods: ARROW is a decentralised, Phase 3 randomised, double-blind, placebo-controlled trial. We aim to recruit and follow-up 870 children aged 1 to < 6 years. Participants are randomised to 3.5 mg of OM-85 or placebo daily for the first 10 days of every month, for 12 months. Health professionals from over 40 hospitals participating in the Children's Inpatient Research Collaboration of Australia and New Zealand (CIRCAN) invite families to the ARROW trial. The ARROW central team organises enrolment, randomisation, medication distribution, and follow-up, conducting these activities entirely remotely in Australia and both remotely and in-person in New Zealand. Ethics and Dissemination: ARROW received ethics approval from The Royal Children's Hospital Human Research Ethics Committee in Australia and the Health and Disability Ethics Committee in New Zealand. Findings will be published in peer-reviewed international journals. Trial registration: ANZCTR: ACTRN12620001370998 (Registered on 21 December 2020).