This chart shows the primary vaccine coverage ratio across countries by World Bank income classification.
It shows the extensive margin of vaccination (the extent to which countries vaccinate at all, which is represented by the circular inner and outer bars) and the intensive margin (the actual level of the coverage ratio, which is represented by the vertical bars for each country). Note that as for the extensive margin most countries have started the vaccination process when it comes to the primary vaccination cycle, which is why the circular bars are almost entirely blue. But this was not the case earlier as this dynamic version of the chart shows. Note also that universal coverage on both the extensive and intensive margins would amount to this donut turning entirely blue.
The vaccine coverage ratio is calculated as the number of primary doses administered divided by the total population. Full coverage is achieved at 200 primary doses per 100 people. Note that primary doses are the doses administered as per the primary (first) vaccination cycle, which excludes boosters. We distinguish from boosters to be able to compare vaccination progress across countries and country groups during the first round of vaccinations.
One further note on the calculation of the vaccine coverage ratio, which represents a new way of assessing global vaccination progress that yields consistent comparisons across countries invariant to the mix of vaccines used. The method employed is to convert all primary doses administered into double-dose equivalents. That means that doses belonging to 1-dose protocols are multiplied by 2 whereas doses belonging to 3-dose protocols are multiplied by 2/3. With this adjustment, we achieve 200 as the full coverage milestone for primary vaccinations.
For further details on the adjustment method, check out this post and the background note below on double-dose equivalents and other aspects (e.g. extensive and intensive margins, World Bank income classification and the universe of countries).