This chart shows the vaccine coverage ratios for the world and across World Bank regions distinguishing between primary vaccines (bars) and boosters (dots). Each coverage ratio is calculated as the number of doses administered divided by the total population.
There is however one more twist. The vaccine coverage ratio for primary doses represents a new way of assessing global vaccination progress that yields consistent comparisons across countries that are 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.
No such adjustment is made to boosters which (as of now) require only a single shot. The full coverage milestone for boosters is therefore 100.
For further details on the adjustment method, check out this post and the background note below on double-dose equivalents and other aspects such as the country classification and the universe of countries.