Blood type may contribute to likelihood of acquiring COVID-19
A patient’s blood type plays a role in the likelihood of developing COVID-19, data from two genetic studies show.
An infectious disease expert unaffiliated with the studies told Healio Primary Care that the results are possible, but with some important caveats.
In the first study, which appeared in The New England Journal of Medicine, David Ellinghaus, a scientist at the Institute of Clinical Molecular Biology in Germany, and colleagues analyzed nearly 8.6 million single nucleotide polymorphisms from 1,610 Spanish and Italian patients with COVID-19 and respiratory failure. Another 2,205 uninfected participants served as controls. Participants’ age, ethnicity and sex were also part of the analysis.
They found that participants with blood type A had a higher risk for acquiring COVID-19 with respiratory failure than other blood types (OR = 1.45; 95% CI, 1.2-1.75, P = 1.48 × 10-4). The researchers also observed a protective effect in blood group O vs. other blood groups (OR = 0.65; 95% CI, 0.53-0.79, P = 1.06 × 10-5).
Though Ellinghaus called the findings “remarkable,” he also said other COVID-19 risk factors have far greater influence.
“A previous study by researchers from Grossman School of Medicine in New York showed the strongest hospitalization risks were in individuals aged 75 years and older had an estimated odds ratio of 66.8,” he told Healio Primary Care. “This same study showed that comorbidities are strong predictors of hospitalization and admission; on the other hand, oxygen impairment and markers of inflammation were most strongly associated with critical illness.”
Ellinghaus said “it is currently difficult to make a suitable recommendation as to what exactly can be done” in clinical practice regarding the blood type findings.
In the second study, Adam Auton, PhD, principal scientist at 23andMe, and colleagues analyzed genetic data from more than 800,000 of the company’s customers.
“Participation was completely voluntary, and customers can withdraw consent at any time,” he said in an interview.
Auton and colleagues also found that type O blood showed a protective effect against acquiring the virus vs. all other blood types (OR = 0.86; P < .0001). Patients with that blood type were also less likely to be hospitalized with COVID-19 (OR = 0.81; P = .05). Adjustments for patients’ age, BMI, comorbidities, ethnicity and sex had no bearing on the findings, according to the researchers.
Auton told Bloomberg News that the results should be interpreted with caution until additional research is completed.
The company Ancestry is also conducting a genetic analysis of 600,000 willing customers. Catherine Ball, PhD, Ancestry’s chief scientific officer, declined to share their findings until they can be analyzed by researchers, but she said that even if the results show that blood type plays a role in the risk for acquiring COVID-19, they will only solve one piece of a larger puzzle.
“The answer to COVID-19’s cause is likely much more complicated than what a patient’s blood type is,” Ball told Healio Primary Care. “That answer likely involves hundreds, perhaps thousands of different parts of the genome are interacting in a complicated way.”
Gregory A. Poland, MD, director of the vaccine research group at Mayo Clinic, agreed.
“There are multiple factors associated with coronavirus infection and disease severity,” he told Healio Primary Care. “For example, hypertension has a risk factor of 2. The Ellinghaus paper showed blood type’s risk factor was less than that. Blood type may be is one of many factors that together determine how severe your disease is going to be and whether you're going to survive COVID-19.”
Poland, who was uninvolved in the research, noted that the Ellinghaus paper cohort was small.
He also said some of the reported P values in the NEJM and 23andMe.com studies “barely meet” statistical significance, explaining that P values of 10-8 or greater are preferred. “The findings have some biologic plausibility but need to be confirmed in studies that can more precisely account for a variety of statistical and clinical factors,” he said.
Poland also noted that the NEJM and 23andme.com studies are genetic association studies that should not be interpreted as a cause and effect finding. “Further mechanistic validation studies would be required before cause and effect could be claimed,” he said. “Nonetheless, the findings are worthwhile and add more credence that blood type among other factors, could be important prognostic factors.
- 23andMe. 23andMe finds evidence that blood type plays a role in COVID-19.
- Brown KV. 23andMe provides more evidence that blood type plays role in virus. Bloomberg News. June 8, 2020.