I believe the way to read that is that it's inverse because:
high functioning thymus = low severity
low functioning thymus = high severity
So the further reduced it was, the more severe the outcome.
Correct. So it's inverse because when the thymus is high functioning, the disease is low severity. When the thymus is low functioning, the disease is high severity.
@BE @ChristosArgyrop I believe the severity of the disease refers to severity of the COVID-19 disease.