Introduction Recent studies suggest that the high mortality rate of respiratory viral infections is a result of an overactive neutrophilic inflammatory response. Macrolides have anti-inflammatory properties, including the ability to downregulate the inflammatory cascade, attenuate excessive cytokine production in viral infections, and may reduce virus-related exacerbations. In this study, we will test the hypothesis that prophylactic macrolides will reduce the severity of respiratory viral illness in children with chronic lung disease by preventing the full activation of the inflammatory cascade.

Methods and analysis A randomised double-blind placebo-controlled trial that will enrol 92 children to receive either azithromycin or placebo for a period of 3–6 months during two respiratory syncytial virus (RSV) seasons (2015–2016 and 2016–2017). We expect a reduction of at least 20% in the total number of days of unscheduled face-to-face encounters in the treatment group as compared with placebo group. Standard frequentist and Bayesian analyses will be performed using an intent-to-treat approach.

Discussion We predict that the prophylactic use of azithromycin will reduce the morbidity associated with respiratory viral infections during the winter season in patients with chronic lung disease as evidenced by a reduction in the total number of days with unscheduled face-to-face provider encounters.

Ethics and dissemination This research study was approved by the Institutional Review Board of the University of Texas Health Science Center in Houston on 9 October 2014. On completion, the results will be published.

Trial registration number NCT02544984.