Excellent question! It is absolutely possible that a vaccine did not make it into an EHR and for whatever reason the patient stated that they were not vaccinated when asked. Sometimes a patient is unable to speak for themselves and a family member will be asked, the family member can certainly be wrong.
Assuming the numbers are correct, there are a lot of factors that can affect the proportions of vaccinated vs unvaccinated hospitalizations. First, we're the highest acuity hospital in our area. We're also a public "safety net" hospital. We get the sickest patients, we get the patients on medicaid/medicare, and we get the patients that are uninsured.
For more information, we have 98 adult ICU beds. Having just over 20% of those be occupied by COVID patients actually puts us quite a bit below the national average, and it's a lower percentage than the other hospitals in our area. I don't have specific numbers for the vaccine status of the other hospitals. I do know that in our county, the number of hospitalized patients are split about 50/50 between vaccinated and unvaccinated. In the month of November, about 68% of deaths were among the unvaccinated.
Another assumption you might be making is that all patients that succumb are in the ICU. That simply isn't true. Many die in the ED, some die in med/surg units, and some die at home. More than half of those unvaccinated ICU patients will be discharged.
It's hard to take a look at one hospital and compare it to national data, because there are a lot of factors at play. We're one data point and you have the numbers from one day.