Funding for this research was provided by:
Horizon 2020 (101003688)
Received: 3 April 2020
Accepted: 17 April 2020
First Online: 7 May 2020
Ethics approval and consent to participate
: Participation in this opt-in study was voluntary, and all analyses were carried out on anonymised data. The study and method of informed consent were approved by the ethics committee of the London School of Hygiene & Tropical Medicine reference number 21795.
: Not applicable
: WJE is a member of the Editorial Board of this Journal. Other authors declare that they have no competing interests.