Temporal inequalities in the global COVID-19 vaccine rollout: a cross-national observational study of delivery, health-system capacity, and time to coverage
- 1Lehigh University
Abstract
IntroductionBy the end of 2023, many low-income countries had not reached 50% COVID-19 vaccine coverage, while most high-income countries had exceeded 80%. It remains unclear whether receiving vaccine deliveries translated into faster population coverage. We examined cross-national inequalities in the timing of the vaccine rollout and whether deliveries through the COVID-19 Vaccines Global Access (COVAX) facility were associated with subsequent national uptake.
MethodsWe conducted an observational study of 218 countries and territories using country-level data up to December 2023. We used generalized additive mixed models to identify country-level correlates of coverage at an early and a later stage of the pandemic, survival analysis to compare the time to 50% coverage between COVAX Advance Market Commitment (AMC) and non-AMC countries, and an event study to estimate the association between the timing of the first COVAX delivery and subsequent monthly coverage in AMC countries.
ResultsAMC-supported countries reached 50% coverage substantially more slowly than non-AMC countries. The hazard of reaching the threshold was 0.17 times that of non-AMC countries at month 1 (95% CI 0.07 to 0.41) and 0.53 times at month 18 (95% CI 0.33 to 0.85). One year after rollout began, 65.9% of AMC countries (95% CI 56.7 to 76.6) had not reached 50% coverage, compared with 21.1% of non-AMC countries (95% CI 15.1 to 29.5). The timing of COVAX deliveries was not significantly associated with subsequent national uptake in any post-delivery month. In the early stage of rollout, higher maternal mortality was associated with lower coverage, while a larger urban population was associated with higher coverage. By the end of the observation period, larger household size was associated with lower coverage, while higher health expenditure and a larger urban population were associated with higher coverage.
ConclusionReceiving COVAX deliveries was not, on its own, associated with faster coverage. Coverage differences were more consistently associated with country-level structural and health-system characteristics, while we found no significant association with the timing of the first COVAX delivery. Achieving vaccine equality likely requires strengthening the capacity of health systems to convert deliveries into administered doses, and preparedness efforts should invest in last-mile delivery capacity ahead of future emergencies.
Key messagesO_ST_ABSWhat is already known on this topicC_ST_ABSLow-income countries lagged far behind high-income countries in COVID-19 vaccine coverage, and although COVAX was created to narrow this gap, few studies examined whether receiving deliveries translated into faster population uptake.
What this study addsAcross 218 countries and territories, AMC-supported countries reached 50% coverage substantially more slowly than non-AMC countries, and the timing of COVAX deliveries showed no significant association with subsequent national uptake. Coverage was more consistently associated with country-level structural factors, namely maternal mortality and urban population in the early stage and household size, health expenditure and urban population by the end of the period.
How this study might affect research, practice or policyVaccine delivery alone may be insufficient to accelerate coverage. Preparedness efforts should invest in the health-system capacity needed to convert deliveries into administered doses, and should measure success by how quickly populations are protected rather than by doses shipped.
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BibTeX
@misc{lee2026temporal,
title = {{Temporal inequalities in the global COVID-19 vaccine rollout: a cross-national observational study of delivery, health-system capacity, and time to coverage}},
author = {H.-W. Lee and Y.-H. Huang and T. C. McAndrew},
howpublished = {medRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.29.26361724},
url = {https://www.medrxiv.org/content/10.64898/2026.08.29.26361724v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Temporal inequalities in the global COVID-19 vaccine rollout: a cross-national observational study of delivery, health-system capacity, and time to coverage
AU - H.-W. Lee
AU - Y.-H. Huang
AU - T. C. McAndrew
PY - 2026
DA - 2026/08/29
PB - medRxiv
DO - 10.64898/2026.08.29.26361724
UR - https://www.medrxiv.org/content/10.64898/2026.08.29.26361724v1
AB - IntroductionBy the end of 2023, many low-income countries had not reached 50% COVID-19 vaccine coverage, while most high-income countries had exceeded 80%. It remains unclear whether receiving vaccine deliveries translated into faster population coverage. We examined cross-national inequalities in the timing of the vaccine rollout and whether deliveries through the COVID-19 Vaccines Global Access (COVAX) facility were associated with subsequent national uptake. MethodsWe conducted an observational study of 218 countries and territories using country-level data up to December 2023. We used generalized additive mixed models to identify country-level correlates of coverage at an early and a later stage of the pandemic, survival analysis to compare the time to 50% coverage between COVAX Advance Market Commitment (AMC) and non-AMC countries, and an event study to estimate the association between the timing of the first COVAX delivery and subsequent monthly coverage in AMC countries. ResultsAMC-supported countries reached 50% coverage substantially more slowly than non-AMC countries. The hazard of reaching the threshold was 0.17 times that of non-AMC countries at month 1 (95% CI 0.07 to 0.41) and 0.53 times at month 18 (95% CI 0.33 to 0.85). One year after rollout began, 65.9% of AMC countries (95% CI 56.7 to 76.6) had not reached 50% coverage, compared with 21.1% of non-AMC countries (95% CI 15.1 to 29.5). The timing of COVAX deliveries was not significantly associated with subsequent national uptake in any post-delivery month. In the early stage of rollout, higher maternal mortality was associated with lower coverage, while a larger urban population was associated with higher coverage. By the end of the observation period, larger household size was associated with lower coverage, while higher health expenditure and a larger urban population were associated with higher coverage. ConclusionReceiving COVAX deliveries was not, on its own, associated with faster coverage. Coverage differences were more consistently associated with country-level structural and health-system characteristics, while we found no significant association with the timing of the first COVAX delivery. Achieving vaccine equality likely requires strengthening the capacity of health systems to convert deliveries into administered doses, and preparedness efforts should invest in last-mile delivery capacity ahead of future emergencies. Key messagesO_ST_ABSWhat is already known on this topicC_ST_ABSLow-income countries lagged far behind high-income countries in COVID-19 vaccine coverage, and although COVAX was created to narrow this gap, few studies examined whether receiving deliveries translated into faster population uptake. What this study addsAcross 218 countries and territories, AMC-supported countries reached 50% coverage substantially more slowly than non-AMC countries, and the timing of COVAX deliveries showed no significant association with subsequent national uptake. Coverage was more consistently associated with country-level structural factors, namely maternal mortality and urban population in the early stage and household size, health expenditure and urban population by the end of the period. How this study might affect research, practice or policyVaccine delivery alone may be insufficient to accelerate coverage. Preparedness efforts should invest in the health-system capacity needed to convert deliveries into administered doses, and should measure success by how quickly populations are protected rather than by doses shipped.
ER -