1. Authors’ affiliations 1 Department of Health Policy, London School of Economics and Political Science, London, UK.
2. Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK.
3. Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
4. Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.