If somebody comes in the ICU with COVID symptoms, it's extremely likely that they were hospitalized earlier and thus their vaccination status is known. If some

If somebody comes in the ICU with COVID symptoms, it's extremely likely that they were hospitalized earlier and thus their vaccination status is known. If somebody comes in the ICU without non-COVID symptoms, they aren't in the statistic, in other words you need to make the probability of "unknown status" conditional on being in the ICU for COVID.