Study design
The CHICO (CHIldren’s COugh) randomised controlled trial was an efficient, pragmatic, open label, two arm (intervention versus usual care) trial of children aged 0-9, clustered by primary care practices in England. The trial included an embedded qualitative study that will be reported in detail elsewhere and a health economic analysis. The CHICO trial randomised practices between October 2018 and October 2020, with a trial data collection period from November 2018 to September 2021, thus including the covid-19 pandemic that began in March 2020 and was still ongoing in September 2021. We recruited practices by using clinical commissioning groups (CCGs; renamed integrated care boards from 1 July 2022) and the National Institute for Health and Care Research’s Clinical Research Network. We did an internal pilot in three CCGs initially to identify any problems with the intervention. This lasted three months and included a further four CCGs to help to establish best practice for recruiting and communicating with practices before widening to the remaining CCGs. The trial protocol has been published.