Does Blood Type O Protect Against COVID-19? What Research Shows

Research update — 9 October 2026: This article was originally published in June 2020, when early studies prompted headlines about blood groups and COVID-19. The original article has been rewritten to reflect later systematic reviews. Blood type does not make anyone immune to SARS-CoV-2, and it should not be used to make personal health decisions.

Why researchers examined blood groups

Early COVID-19 research asked whether ABO blood groups were associated with differences in infection risk. ABO groups reflect the presence or absence of particular markers on red blood cells. Researchers can compare infection rates across large populations, but identifying an association is not the same as showing that a blood group itself prevents infection.

A 2021 systematic review and meta-analysis of 21 studies found a lower observed infection rate among people with group O than among people with non-O groups. The authors also described the quality of the evidence for lower susceptibility as low or very low and reported no demonstrated effect on disease severity. Such findings may reflect complex biological and study-design factors, not a dependable personal shield.

What later evidence added

A subsequent systematic review focused on whether blood group O reduces the risk of serious COVID-19 outcomes. Of 17 relevant studies reviewed, most reported no significant relationship between group O and severity. The authors concluded that the best available evidence did not support the claim that group O protects people from serious outcomes.

A separate review of ABO/Rh groups and infection risk reported associations across observational studies, while also finding substantial differences between studies. These results can support further research into possible mechanisms, but they cannot tell an individual whether they are safe from infection.

How to interpret the headlines

• Association is not immunity. A small average difference between study groups does not mean that an individual in one group cannot catch a virus.
• Infection and severity are distinct outcomes. Evidence suggesting a group-level association with infection does not automatically establish protection against hospitalization or serious disease.
• Research findings evolve. The strongest interpretation incorporates later analyses and openly acknowledges uncertainty and conflicting results.

The practical takeaway is simple: knowing your blood group may be medically useful for transfusions and other care, but it is not an alternative to evidence-based public-health advice or clinical assessment. A sensational blood-type headline should never be treated as a promise of protection.

Research sources

• ABO blood group and COVID-19: updated systematic review and meta-analysis (2021).
• Best Evidence Topic report on blood group O and severe COVID-19 (2024).
• Systematic review of ABO/Rh blood groups and infection risk (2023).

Editorial transparency: The previous 2020 version credited a Jerusalem Post news report and contained stronger protective-language claims. This updated version replaces those claims with an independently written evidence review linked to the underlying medical literature.