Question & Answer

Does blood type affect your risk of contracting COVID 19?

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  • You are born with a particular blood group or type: A, B, AB or O.
  • There has been interest across traditional and social media in whether a person’s blood type is associated with the risk of contracting COVID-19.
  • There is no evidence that blood type is associated with increased COVID-19 severity.
  • The evidence on whether a person’s blood type is associated with risk of contracting COVID-19 is inconclusive, because only a few studies have been carried out to examine this claim and any differences that have been found between blood groups have been small.
  • At the time of our search, two studies from the US, one study from China and one study from the UK had examined this question.
  • A study which looked at the blood group of patients diagnosed with COVID-19 in a New York hospital, found higher numbers of patients with blood group B and a lower numbers of patients with blood group O, when compared to patients not diagnosed with COVID-19 attending the same hospital. However, differences in patients such as age, sex, blood pressure, diabetes, weight, and chronic cardiovascular and lung disorders could influence these rates. When these factors were taken into consideration by the authors this difference between the blood groups did not remain.  
  • The US study also combined their data with data from studies conducted in China and the UK. These results demonstrated a greater proportion of Type B blood groups and lower proportion of Type O blood groups among COVID-19 patients compared to people who tested negative.
  • A further small observational study observed that patients in a US hospital with blood types B and AB who received a COVID-19 test were more likely to test positive and those with blood type O were less likely to test positive.
  • Two small observational studies in the UK and China found that those with blood type A were more likely to test positive for Covid-19. Patients with blood type O were less likely to be diagnosed with COVID-19 than those with other blood types. Blood type was not associated with hospitalisation among those diagnosed with COVID-19.
  • In summary, the evidence on whether blood type is associated with a person’s risk of contracting COVID-19 is to protect yourself and others from coronavirus, please continue to follow public health advice to maintain social distancing and wash your hands properly and often.
 

Things to Remember

  • Beware of claims based on a single study. Ask if there are other studies that examine the same question and a careful summary of all the relevant studies.
  • Beware of claims that are based on before and after comparisons and when people don’t say what a treatment was compared to. Remember: Ask what the treatment was compared to, and whether it was a fair comparison.
  • Whenever possible, use up-to-date careful summaries (systematic reviews) of fair comparisons to inform decisions.

Reviewers

  • Lead Researcher: Dr Chris Noone, School of Psychology, NUI Galway
  • Reviewed by: Elaine Finucane, HRB-Trials Methodology Research Network, School of nursing and Midwifery, NUI Galway.
  • Evidence Advisor: Dr Maureen Kelly, College of Medicine, Nursing and Health Sciences NUI Galway
  • Evidence Advisor: Casey Donaghey, PPI Ignite, NUI Galway
  • Journalist Advisor: Dr Claire O’Connell, Contributor, The Irish Times