Vaccine rollout is the process of distributing vaccines to populations and ensuring widespread vaccination. This is a crucial part of fighting pandemics and preventing outbreaks. Despite the enormous challenges of vaccine development, rollout has been exceptionally rapid compared to previous pandemics: high income countries reached 20 percent coverage in months rather than years, and even middle-income countries reached 10 percent within a few weeks.

The COVAX initiative has allocated over 170 million doses of vaccines to 138 countries around the world, prioritising them by population group and by a combination of threat and vulnerability factors. These allocations were made using a model that has been vetted by ethicists and scientists, and is intended to ensure that the vaccines reach those most at risk of infection or death from the virus.

Numerous modelling works have analysed different distribution strategies for the vaccine in the context of the COVID-19 pandemic (Bubar et al, 2020; Buckner et al, 2021; Chen et al, 2020; Hogan et al, 2021; Matrajt et al, 2021). The results of these analyses suggest that prioritising groups with higher mortality per infection or interactions can lead to significant reductions in fatalities compared to vaccination with no group priority.

These results are also valid when children are not eligible for vaccination. In this case, prioritising groups with high daily person-to-person interactions still leads to better outcomes and less fatalities than a strategy without priority, but the differences are much smaller.