Financial & competing interests disclosure
Charles D Mackenzie is supported in part by a grant from the Bill and Melinda Gates Foundation (Seattle, WA, USA). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.