Some quick points:
- Reported odds ratios[0] of 1.2 for A and 0.67 for O.
- This is a preprint, so it has not been peer reviewed.
- They compared blood type of patients with that of the general population in the region.
- Data is from 2,173 patients at three hospitals. The data varied between them, but Wuhan had the overwhelming majority (1,775, or 81%) of cases.
- Since these are all patients, they presumably are weighted toward the more extreme responses. There were minimal age and gender differences, though.
- A similar response for type O was apparently reported for SARS.