It's been mentioned before on this thread that it can be hard to interpret vaccination numbers if you don't know what they're based on. I see a fair number of reports on the CBC which mention both sets of numbers.One needs to be a bit careful when comparing percentages vaccinated. The UK Government tends to only publish % of the adult population rather than % of total population. The official figures released today are 88.4% received first vaccination and 71.8% both, but that is of the adult population.
When you are looking at international comparisons then it gets more confusing. In Canadian terms put what you called "adult population" is referred to as "eligible population", because it includes people who are not adults, as we are vaccinating people down to age 12. In other countries the lower age limit might be 18, 16, 15, or 12.
Some countries interpret the lower age limit as being with respect to what age you are right now, while others interpret it as being what age you will be by the end of the year. So for example, earlier this year we were vaccinating people down to age 18, but "18" also meant people who were 17 but would be 18 by the end of this calendar year.
You also have to take into account the fact that countries which have a younger population will have a larger proportion of them who fall below the lower age limit, whatever that may be.
What it means is that if you are doing international comparisons of vaccination coverage then you really can only look at percentage of total population. However, that number will incorporate policy decisions as to age group to vaccinate as well as how well organised the vaccination program is, what their vaccine supply situation is, and how well the population are accepting vaccination.