Funding for this research was provided by:
Wellcome Trust (107731/Z/15/Z)
Royal Society (107731/Z/15/Z)
Text and Data Mining valid from 2018-10-22
Received: 13 March 2018
Accepted: 14 October 2018
First Online: 22 October 2018
Ethics approval and consent to participate
: The protocol for this study was approved by the MHRA Independent Scientific Advisory Committee (ISAC) (protocol number 16_163; protocol included as Additional file InternalRef removed: Protocol), and the study was approved by the London School of Hygiene and Tropical Medicine MSc Ethics Committee (approval number 10700). Participant consent is not required for ISAC approved CPRD studies using purely observational data.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.