1. UCL Research Department of Primary Care & Population Health, Royal Free Hospital, Rowland Hill Street, London NW3 2PF, UK
2. School of Social Sciences, Birmingham City University, 4 Cardigan Street, Birmingham B4 7BD, UK
3. Rapid Research Evaluation and Appraisal Lab (RREAL), Department of Targeted Intervention, University College London (UCL), Charles Bell House, 43–45 Foley Street, London W1W 7TY, UK
4. Vaccines and Society Unit, Oxford Vaccine Group, Oxford University, Oxford OX3 7LE, UK
5. Patient and Public Involvement Authors, UCL Research Department of Primary Care & Population Health, Royal Free Hospital, Rowland Hill Street, London NW3 2PF, UK
6. Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK