| Authors contributions | |
| Nigel Rollins | Design, implementation and project management of the study, analysis of data and drafted manuscript |
| Renaud Becquet | Analysis of data and drafted manuscript |
| Ruth Bland | Design, implementation and project management of the study, analysis of data and reviewed manuscript |
| Anna Coutsoudis | Conceptualisation, design and implementation of the study, and drafted the manuscript |
| Hoosen Coovadia | Conceptualisation, design and implementation of the study, and drafted the manuscript |
| Marie-Louise Newell | Design of study, analysis of data and drafted manuscript |