Blood Type Does Not Affect Risk of COVID-19 or COVID-19 Mortality
Key findings
- According to Boston data and re-analysis of data from China, there is no association between ABO blood group and death from COVID-19
- The U.S. data did not support the conclusion by Chinese researchers that individuals with blood type A are at greater risk of SARS-CoV-2 infection than people with other blood types
- In Boston, blood type O was slightly more common in COVID-19 patients than in patients hospitalized before the pandemic, perhaps because the pandemic has disproportionately affected Latinx people in Boston, among whom type O is more frequent
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Because of the wide range of severity of COVID-19, it's suspected that host factors—perhaps including genetic factors—influence clinical outcomes. Blood type may be one of those genetic factors.
Data from a large study in China, presented in a non–peer-reviewed preprint paper, showed that blood type O was significantly less common, and blood type A was significantly more common, among 1,775 hospitalized patients with COVID-19, as compared to 3,694 healthy population-based controls. In addition, type O was significantly less common in COVID-19 patients who died than in healthy controls.
Crystal M. North, MD, MPH, physician in the Division of Pulmonary and Critical Care Medicine at Massachusetts General Hospital, Walter "Sunny" Dzik, MD, co-director, Blood Transfusion Service at Mass General, and colleagues re-analyzed the Chinese data and conducted similar analyses of patients in Boston. In a letter to the editor of Transfusion, they report no significant influence of ABO blood type on COVID-19 mortality or the risk of SARS-CoV-2 infection.
Reconsidering the Chinese Data
A more meaningful investigation than comparing COVID-19 patients with healthy controls, the researchers note, is to evaluate ABO blood types in COVID-19 patients who survived and those who died. Re-analyzing the Chinese data that way, they found no association between ABO distribution and death.
Blood Type and Survival
The team then examined ABO blood types among 957 patients who were hospitalized with confirmed COVID-19 at Mass General or Brigham and Women's Hospital in Boston between February 12 and May 13, 2020. When the survivors were compared with the 135 non-survivors, there was no association between ABO distribution and fatal outcome.
Blood Type and Risk of Infection
ABO blood type varies by ethnicity, and the researchers wondered whether ethnicity influences ABO distribution in cohorts with and without COVID-19. They compared the same 957 patients with 5,840 randomly selected patients hospitalized between March and April 2019, well before COVID-19.
The proportion of individuals with type O was slightly higher in the group of COVID-19 patients (49%) than in the other group (47%), but the difference was not statistically significant. In Boston, the pandemic has disproportionately affected Latinx people, among whom type O is more frequent.
Whatever the explanation for the latter results, this study does not support the conclusion by other researchers that individuals with blood type A are at greater risk of SARS-CoV-2 infection than people with other blood types.
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