It is intentionally very hard to know, since it was decided from the beginning by the CDC to basically not report "breakthrough infections" unless the "vaccinated" people are hospitalized or die from their "infection". Also it was strongly encouraged to subject "vaccinated" PCR to fewer cycles, creating fewer false positives compared with the higher threshold for "unvaccinated".

And yet WaPo still practically saying here it's wrong to count "breakthrough infections" among vaccinated with no strong symptoms or illness. If it's wrong for them it's wrong for the "unvaccinated" too.