Which countries? I find it hard to get data at vaccination prevalence in ICU population specifically, but in Switzerland, the figures I see cited is 60-70% of patients unvaccinated (With 90% of 80%+ year olds in the population being double vaccinated).
For the 80+ group the latest data for hospitalisations is 47% vaccinated, 31% non-vaccinated, 22% unkown.
If you look at the total value, it appears that only 11 % of hospitalized are double vaccinated, though the latest seven day average puts that number at 27 %.
For the broad population is 28% vaccinated vs 57% non-vaccinated. The remaining 15% is "unknown". But Switzerland has a relatively low vaccination rate at 67%.
Edit: looking at deaths instead of hospitalisations in the broad population:
Fully-vaccinated 46%, partially-vaccinated 2%
Non-vaccinated 41%
Unknown 12%Edit: I can't find ICU numbers but the latest death stats for 80+ are 46% vaccinated, 33% non-vaccinated, 21% unknown.