Question: I read some headlines again mentioning blood type and COVID. What’s the latest?

Answer: We last talked about blood type and COVID in our Q&A of 6/23 #Blood Type. A new study was published in the New England Journal of Medicine just today that sheds more light on the association between blood type and severe COVID outcomes, “Genomewide Association Study of Severe Covid-19 with Respiratory Failure” (described further in the paragraph below). Similar to what we discussed back in June, authors report, “In the meta-analysis corrected for age and sex, we found a higher risk among persons with blood group A than among patients with other blood groups (odds ratio, 1.45; 95% CI, 1.20 to 1.75; P=1.48×10−4) and a protective effect for blood group O as compared with the other blood groups (odds ratio, 0.65; 95% CI, 0.53 to 0.79; P=1.06×10−5)….Our genetic data confirm that blood group O is associated with a risk of acquiring Covid-19 that was lower than that in non-O blood groups, whereas blood group A was associated with a higher risk than non-A blood groups.”

In this case-control study, researchers recruited 1980 patients with severe Covid-19 — defined as hospitalized with respiratory failure (e.g. oxygen supplementation or mechanical ventilation) and COVID-19 confirmed with positive PCR test — from seven hospitals in Italy and Spain (cases). They also recruited 2381 control participants from Italy and Spain, the majority of whom were healthy blood donors (controls). Researchers then extracted DNA from participant samples and compared genomic sequencing between cases and controls to understand whether people who experienced severe COVID-19 had genetic susceptibility — controlling for age, sex, and underlying conditions — comparing those with the most severe outcomes (mechanical ventilation) with less severe outcomes (oxygen supplementation) AND comparing all cases with all controls.