Niccolò Meriggi’s research highlights how cost-effective models prioritising accessibility can revolutionise rural vaccinations.

Postdoctoral Research Fellow at the Department of Economics and the CSAE, Niccolò Meriggi and co-authors have published a study titled, ‘Last-mile Delivery Increases Vaccine Uptake in Sierra Leone’ in which they designed a cost-effective strategy to enhance COVID-19 vaccination rates.

The research introduces a simple yet widely applicable intervention to enhance vaccine accessibility, and it was conducted by a collaborative team of academic institutions, including the International Growth Centre, University of Oxford, Yale University School of Management, and Wageningen University, and policymakers at the Ministry of Health and Sanitation and Concern Worldwide.

Niccolò summarises the study stating: “Our research shows that access was a binding constraint to the COVID-19 vaccination campaign in remote areas of Sierra Leone. Access is crucial to achieving vaccine equity in developing countries, and will likely be relevant to the new malaria vaccine roll-out and other health products and services.”

The team used mobile vaccination sites, and this initiative cost 76% less than comparable models (approximately $80) and was incredibly successful; within 48-72 hours, vaccination rates in the treatment group increased by 26 percentage points, with a sevenfold rise in vaccination counts. By December 2022, Sierra Leone had achieved the World Health Organisation's global target, immunising 70% of its adult population against COVID-19.

This cost-effective model has the potential for replication across developing countries with large rural populations and similar transport, community, and infrastructure setups. The model's efficiency stems from its ability to leverage existing clinic infrastructures, effectively reaching underserved communities.

Looking ahead, the research team, led by principal investigator Niccolò F. Meriggi, plans to expand the successful model to encompass a broader spectrum of health products and services. Securing grants totalling US$ 672,000 from the US-based Social Science Research Council through its Mercury Project and GBP 100,000 from the International Growth Centre, the team aims to explore the feasibility and cost-effectiveness of the model when applied to additional vaccines and maternal and child health interventions.



Find out more about the study below:

Access the paper: Last-mile delivery increases vaccine uptake in Sierra Leone - ORA - Oxford University Research Archive


Media engagement:

Mobile delivery of COVID-19 vaccines improved uptake in rural Sierra Leone (

Going the Last Mile (with Evidence) | Yale Insights

“Last mile” solutions increase vaccination coverage in poor countries - WUR

Last mile delivery vaccine uptake in Sierra Leone | International Growth Centre (

Ground-breaking research unveils cost-effective model to boost COVID-19 immunisation in developing countries | University of Oxford

Niccolò’s interview on German Radio:

Niccolò’s interview with Italian Radio: