Socioeconomic determinants potentially underlying differential global SARS-CoV-2 testing capacity: an ecological study.

Objectives: To analyse the relationships between SARS-CoV-2 laboratory testing capacity (TC) and socioeconomic factors (wealth, governance and social inequality) across 109 countries in 2020-2021, to identify potential determinants of global disparities in TC during the COVID-19 pandemic.

Design: An ecological study using regression analyses to explore the associations between TC and socioeconomic determinants within and across global regions.

Setting/participants: Data from 109 countries from Our World in Data, the WHO, the United Nations and others grouped into six geographic and sociodemographic regions (global burden of disease regions), were analysed separately for the years 2020-2021 based on differential vaccine availability and country-level responses throughout the pandemic.

Outcome Measures: Relationships between SARS-CoV-2 TC and factors such as vaccination rates, wealth, vulnerable employment (VE), gender and income inequality within and across world regions in 2020-2021.

Results: TC increased a minimum of 2.1-fold for 'Sub-Sahara' (median TC 1800-3700 tests) to a maximum of 4.9-fold for 'Asia and Oceania' (4500-22 000) between 2020 and 2021. Factors associated with TC among the socioeconomic variables included VE that was associated with reduced TC both in 2020 (relative change (RC) -43%; 95% CI -57% to -25%) and 2021 (RC -46%; 95% CI -62% to -24%) and employment-to-population ratio that had a positive effect on TC in 2021 (RC 27%; 95% CI 44% to 55%). Socioeconomic variables showed similar patterns for both the established measles-mumps-rubella and the new COVID-19 vaccines. Region-level analyses revealed stark heterogeneity in the associations between socioeconomic variables and TC between the analysed years (2020 vs 2021) and across regions. Region-specific trends showed that in Latin America and Asia/Oceania, TC was linked to health expenditure in both analysed years (RC: 199%; 95% CI 74% to 405%; RC: 142%; 95% CI 67% to 24%). VE was associated with decreased TC in the 'high-income', 'Central Europe' and 'Sub-Saharan' regions.

Conclusions: Socioeconomic and gender inequalities play a significant role in determining SARS-CoV-2 TC. These inequalities underscore the necessity of ensuring equitable access to health services and targeted public health interventions, particularly in resource-limited settings, to improve health outcomes and pandemic preparedness. Socioeconomic and gender disparities can exacerbate health inequalities and hinder the effectiveness of public health policies in a globally interconnected world.