Two recent studies, from Massachusetts General Hospital in Boston and Columbia Presbyterian Hospital in New York City, did not find significant evidence that blood type meaningfully affects COVID-19 risk. Earlier this year, preliminary data suggested that having type A blood increased the odds of infection and falling seriously ill, but new data show that blood type alone does not offer meaningful protection.
The Mass General study looked at COVID-19 data from hospitals across the state of Massachusetts, including 1,289 patients with positive cases and known blood type. Researchers found no association between blood type and any peak inflammatory markers. After multivariable analysis, blood type also was not found to be independently associated with risk of intubation or death. Patients with blood types B and AB who received a COVID-19 test were more likely to test positive and those with type O were less likely to test positive. However, Anahita Dua, MD, the senior author of the study, said that blood type was not something she would consider when judging a patient's risk factor for COVID-19.
"I wouldn't even bring it up," said Dr. Dua.
The study from Columbia Presbyterian examined records of 7,770 patients who tested positive for the coronavirus and found a somewhat lower risk of ventilation for patients with type A blood. Patients with blood type AB appeared to be at a higher risk of ventilation, but the scientists noted that this result may not be reliable due to low numbers of patients with this blood type in their analysis.
"No one should think they're protected," said Nicholas Tatonetti, PhD, who led the Columbia study.