Association between ABO blood group and COVID-19 infection: an updated systematic review and meta-analysis.

The relationship between ABO blood group and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 - coronavirus disease 19 [COVID-19]) infection has been investigated, and several studies have reported discordant findings. This systematic review and meta-analysis study were conducted to investigate the relationship between ABO blood group and COVID-19 infection. The international databases Institute for Scientific Information (ISI)/Web of Science, PubMed, and Scopus were systematically searched from 1 January 2020 through 14 June 2021. Twenty-seven studies met the inclusion criteria for meta-analysis including 23,285 COVID-19 case subjects and 590,593 control subjects. The odds of having each blood group among COVID-19 patients compared with control subjects were calculated. The random effects model was used to obtain the overall pooled odds ratio (OR). Publication bias and subgroup and sensitivity analyses were performed to explore the source of heterogeneity. According to the random effects model, the results indicated that the pooled estimates of OR (95% confidence interval) for blood groups A, O, B, and AB were 1.26 (1.13-1.40), 0.77 (0.71-0.82), 1.05 (0.99-1.12), and 1.11 (0.99-1.25), respectively. Therefore, individuals infected with COVID-19 have higher odds of having blood group A and lower odds of having blood group O. In conclusion, this study indicated that individuals with blood group A are more susceptible to COVID-19 infection, whereas those with blood group O are less susceptible to COVID-19 infection. However, further studies are warranted to support these findings.