Database	Search terms	Date searched
ClinicalTrials.gov (www.clinicaltrials.gov)	cystic fibrosis cystic fibrosis AND vitamin E cystic fibrosis AND tocopherol cystic fibrosis AND toco* cystic fibrosis AND alpha tocopherol	20 July 2020
International Standard Randomised Controlled Trial Number Registry (isrctn.orgctn.org/)	cystic fibrosis cystic fibrosis AND vitamin E cystic fibrosis AND tocopherol cystic fibrosis AND toco* cystic fibrosis AND alpha tocopherol	20 July 2020
WHO clinical trials platform (ICTRP) (apps.who.int/trialsearch/)	cystic fibrosis cystic fibrosis AND vitamin E cystic fibrosis AND tocopherol cystic fibrosis AND toco* cystic fibrosis AND alpha tocopherol	not searched as resource not available due to the Covid‐19 pandemic