This chart shows the evolution over time in the distribution of vaccine doses administered across the World Bank income classification.
Vaccine doses administered refer to total vaccinations, which are defined as adjusted primary doses + boosters. Primary doses pertain to the initial vaccination cycle and are adjusted to take into account the diversity of vaccine protocols. Primary doses of 1- and 3-dose vaccines are adjusted into 2-dose equivalents, which amounts to multiplying them by 2 and 2/3, respectively, before adding them up. This method, further detailed in this post, makes sure that we make correct comparisons across countries and country groups in the doses space.