The researchers also point out that they did not find any significant difference in rate of infection between A, B, and AB blood types.
Their research showed those with blood type A or AB typically had a longer stay in the intensive care unit, with a median of 13.5 days.
Both new studies came out Wednesday in the journal Blood Advances.
It was also found that more patients with groups A and AB needed dialysis for kidney failure.
They said that it can not be assumed that people who are at lower risk of severe illness and death from COVID-19 are also at low risk of ongoing COVID.
Another study, done in Spain compared the outcomes of 1900 severely ill COVID+ patients with 2000 healthy, non-sick patients. Of those, only 38.4% had blood type O - despite people with that blood type making up 41.7% of the roughly 2.2 million untested people in the population.
In this study, researchers analysed data from a Danish health registry that included more than 473 000 patients who were infected with Covid-19 between 27 February 2020 and 30 July 2020.
"Blood group O is significantly associated with reduced susceptibility", the authors wrote.
In general, your blood type depends on the presence or absence of proteins called A and B antigens on the surface of red blood cells - a genetic trait inherited from your parents.
According to the American Red Cross, O-positive is the most common type of blood across all races.
The new studies about blood type and coronavirus risk align with prior research on the topic. An April study, too, (though it has yet to be peer-reviewed) found that among 1,559 coronavirus patients in New York City, a lower proportion than would be expected had Type O blood.
Scientists have been investigating a potential link between blood type and vulnerability to Covid-19 for many months, and this latest evidence supports previous findings.
"I don't think this supersedes other risk factors of severity like age and co-morbities and so forth", Dr. Mypinder Sekhon, who is a clinical assistant professor in the Division of Critical Care Medicine and Department of Medicine at the University of British Columbia told CNN.