Competing interests: The BMJ has judged that there are no disqualifying financial ties to commercial companies. The authors declare the following other interests: PG declares unpaid authorship of a paediatric dermatology guideline commissioned by Johnson and Johnson and receiving travel and accommodation expenses from publishers Jaypee Brothers for giving lectures on paediatrics and research to medical students. ME was paid for consultancy on child health by Oxford Policy Management Group, is? contracted by WHO-AFRO to review child health policies in Africa, and receives funding from Wellcome, NIHR, and UKRI for research on child health. Further details of The BMJ policy on financial interests are here: https://www.bmj.com/sites/default/files/attachments/resources/2016/03/16-current-bmj-education-coi-form.pdf.