Media reports suggested that people’s blood group may affect their chances of infection with coronavirus.

The reports were based on a study which compared blood groups of 2,173 coronavirus patients in hospitals in China with blood groups of 27,080 people from the general population in Wuhan and Shenzhen. The study has not been peer-reviewed or published in a medical journal, but was released early.

The study showed blood type A was more common and type O less common in coronavirus patients than in the general population. But that does not mean blood type directly affects coronavirus infectivity. It could be a co-incidence.

It is not clear how blood type might affect the chances of being infected with coronavirus. Usually, before people accept that something is a risk factor for an illness, we need a biologically-plausible reason why that might be and strong observational research too.

Where did the story come from?

The story first surfaced in the South China Morning Post, which reported on 17 March that “People with blood type A may be more vulnerable to infection by the new coronavirus, while those with type O seem more resistant.”

What is the basis for the claim?

The claims were made in a pre-publication paper by researchers from seven hospitals and universities in Wuhan, Shenzhen and Shanghai, China. The researchers compared the blood group distribution in 2,173 patients with COVID-19 confirmed by SARS-CoV-2 test, from three hospitals in Wuhan and Shenzhen (including 206 who had died), with that of 27,080 people from “recent surveys” of the general population of Wuhan and Shenzhen.

The research reported:

  • 37% of patients with COVID-19 (including 85 who had died) were blood type A, compared to 29% of the general population
  • 26% of patients with COVID-19 (including 52 who had died) were blood type O, compared to 38% of the general population

The researchers calculated that people with blood type A were 21% more likely to be infected than people with other blood types (odds ratio (OR) 1.21, 95% confidence interval (CI) 1.02 to 1.43) and people with blood type O were 33% less likely to be infected than people from other blood groups (OR 0.67, 95% CI 0.60 to 0.75). It is not possible to say if a bias in the way people were selected for this study could have accounted for the apparent difference.

However, the results were not consistent for all 3 hospitals. For one hospital in Shenzhen, people with blood type A were no more likely to be infected than those with other types. This may be because there were fewer patients (285) sampled from this hospital.

 

What do trusted sources say?

The WHO and NHS have not commented on the paper.

Commenting via the Science Media Centre, Dr Sakthi Vaiyapuri, Associate Professor in Cardiovascular and Venom Pharmacology, University of Reading, said: “There is little evidence to substantiate any claim that there [is] any more than a coincidental correlation between blood group ABO and susceptibility of contracting Covid-19.”

He said there were “far too many parameters that cast doubt” on their findings, and added: “Importantly, people should not panic about these results as clearly further scientific research is required to substantiate these claims.”

Analysis by EIU Healthcare, supported by Reckitt Benckiser

 

Citation

1.     Jiao Z et al. Relationship between the ABO Blood Group and the COVID-19 Susceptibility. MedRxiv preprint doi: https://doi.org/10.1101/2020.03.11.20031096. (Accessed 26 March 2020)

Reading list

1.     Science Media Centre. Expert reaction to a preprint on blood type A and COVID-19 susceptibility. https://www.sciencemediacentre.org/expert-reaction-to-a-preprint-on-blood-type-a-and-covid-19-susceptibility/ (Accessed 26 March 2020)