Full vaccination is at about 65%, boosters are at about 25%, lower than much of Europe.
Percent of US Population
At least Fully
one dose Vaxed Boosted
Total 75.4% 63.3% 39.5%
Population ≥ 5 Years of Age 80.1% 67.3%
Population ≥ 12 Years of Age 85.3% 72.1%
Population ≥ 18 Years of Age 87.3% 73.8% 42.6%
Population ≥ 65 Years of Age 95% 88.2% 62.7%
It's reasonable to be measuring against eligibility when evaluating progress in administering boosters, but not being eligible for a booster doesn't really make someone less susceptible to infection, so it isn't the right thing to compare across countries.