[pdabbadabba]

I fear you're committing the baseline fallacy. If 92% of the population is vaccinated then the virus can easily spread mainly among the vaccinated while still spreading among that population at a far lower rate than among the unvaccinated.

Think of it this way: assume that an unvaccinated person, on average, spreads COVID to 10 people and a fully vaccinated person spreads it to only 1. Then put 92 fully vaccinated people and 8 unvaccinated people (I.e., vaccination in proportion to the Icelandic population.) into a room full of people. The 8 unvaccinated people will infect 80 additional people, while the fully vaccinated will infect 92. Thus, "most" of the transmission was from vaccinated people, even though the vaccine reduced transmission by 10x.

And this is probably obvious, but its worth emphasizing that vaccinating those last 8 (percent of the) people would still have a hugely beneficial effect. If they were all vaccinated, then, in the toy example, they would infect a total of only 8 people instead of 80, leading to only 100 total cases, rather than 172.

Of course, even setting this aside, the bigger issue is that your casual parsing of one country's aggregate statistics is just no substitute for the actual scientific research that GP cited.