Funding for this research was provided by:
NIHR Health Protection Research Unit in Immunisation (NIHR200929, NIHR200929, NIHR200929)
Received: 21 June 2021
Accepted: 30 November 2021
First Online: 11 December 2021
: This work was reviewed and approved by the London School of Hygiene and Tropical Medicine Observational/Interventions Research Ethics Committee (Review Reference: 14559) and conforms to the principles of the Declaration of Helsinki. All data was anonymized before analysis took place.
: Not applicable.
: The authors have no competing interests to declair.