It's become evident over the past several months that the body's reaction to the novel coronavirus (COVID-19) is quite varied, with some people experiencing only mild symptoms (or no symptoms at all) and others becoming gravely ill. As for why that range is so wide? You may have heard that it could potentially come down to blood type. "Early reports out of China suggested blood type A predicted a poorer outcome from COVID-19," David Cutler, MD, a family medicine physician at Providence Saint John's Health Centre in Santa Monica, CA, told POPSUGAR.
However, studies since then have been mixed at best. "One retrospective review showed no significant connection between blood type and worsening of the disease," including important markers like the need for hospitalization, Dr. Cutler explained. "An intriguing finding from the study was that there appeared to be a greater chance of people with blood types B and AB who were Rh positive testing positive for the virus," he continued. "Even stronger evidence was assembled by the team that symptomatic people with blood type O were less likely to test positive." Once again, though, Dr. Cutler cautioned that correlation does not imply causation.
Daniel Devine, MD, a dual-board certified internist and geriatrician and cofounder of Devine Concierge Medicine, agreed. "In this study, sample size was relatively small at 483 hospitalized patients and 1,289 total COVID-positive patients who had a blood type documented," Dr. Devine told POPSUGAR. "We need to see more studies with larger numbers of patients to have a better idea if infection rate is increased with certain blood types."
Dr. Cutler added that the research that had previously emerged about blood types and COVID-19 had other limitations. "There are many flaws and biases in these studies," he said. For example, "some studies used blood donors as a comparison group to the COVID-19 patients to look at blood type frequency when COVID-19 is not present. However, it is well known that a disproportionate number of blood donors are type O, as this is the most widely acceptable type of blood for transfusion." Bottom line: early reports aren't conclusive clinical data, and it may be a while before we have the large-scale, long-term studies that would allow experts to draw firm conclusions.
Is There Anything We Can Take Away From These Studies?
"Due to lack of association between blood type and rates of hospitalization, intubation, or death, I feel it is premature to put too much stock in the topic for now," Dr. Devine said. "This newly identified distinction in infection rate between blood types may be a piece of the larger puzzle of COVID-19. It is a starting point for more research into why the virus overexcites the immune system and why the virus causes blood clots in some people and not others."
If anything, the lack of clear answers is an important reminder that we all need to do our best to follow the guidelines issued by experts and be considerate of immunocompromised and at-risk populations. "Other risk factors seem to play a far bigger role in determining outcome from COVID-19, like age. And there are many known risk factors that can be controlled, like smoking and vaping," Dr. Cutler said. "If these dangerous habits are avoided, outcomes would improve. And no blood type assures complete protection from COVID-19 — however, staying six feet away from people, washing your hands, and wearing a mask are proven to offer excellent protection."
Natasha Bhuyan, MD, family physician and regional medical director at One Medical, agreed. "Since we can't change our own blood type, there isn't much use being worried," Dr. Bhuyan told POPSUGAR. "Instead, we should focus on what we can control when it comes to COVID-19: stay at home when you can, wear a mask when you go out, practice good hand hygiene, and stay six feet away from others."