Table 1. Extracted data, variables and data sources.

Concept	Variables	Data source	Used for
COVID-19 prevalence	Country; number of confirmed cases (as of 23/03/2020); number of confirmed deaths (as of 23/03/2020); case fatality rate per 1,000 cases (as of 23/03/2020); order number at which the country experienced the first case (e.g., 1 st country, 2 nd country…)	COVID-19 global surveillance system by Johns Hopkins Univeristy 16, 17	Cluster evaluation
Disease prevalence	Age-standardized prevalence of diabetes, chronic obstructive disease [COPD], HIV/AIDS and tuberculosis (as of year 2017)	2017 Global Burden of Disease / Institute for Health Metrics, Washington University 18	Clustering
Air quality metric	Concentration of 2.5 particulate matter by country	Global Health Observatory data repository, World Health Organization 19	Clustering
Socio-economic metric	Gross domestic product per capita (as of year 2017) a	World Bank 20	Clustering
Health system metric	Universal health coverage index of service coverage (as of year 2017)	Global Health Observatory data repository, World Health Organization 21	Clustering

^aWhen a country did not have data for 2017, we used the latest available; when a country did not have any data on this source, we used data as reported by a Google search (this was the case for four countries).