CDC data show 240 million people with at least one shot, or about 72.5% of the population. But the agency says only 203 million are fully vaccinated, or 61.3%, an 11-percentage-point difference that is far larger than in other developed countries.

State and local officials say it’s improbable that 37 million Americans got one shot without completing their inoculations. Instead, they say, the government has regularly and incorrectly counted booster shots and second doses as first doses.

That means both the fully vaccinated and completely unvaccinated are officially undercounted. The precise number miscounted is unknown, but revisions in data from three states — Illinois, Pennsylvania and West Virginia — found enough over-counting of first shots to indicate millions of unvaccinated people nationally who’ve mistakenly been counted as having received a dose.