Researchers investigated the association of sociodemographic factors and blood group type with the risk of SARS-CoV-2 infection and severity of COVID-19.
Anderson, et al. (2021) acknowledge that, "The observed variability in susceptibility to SARS-CoV-2 and severity of the ensuing COVID-19 have raised intense interest in their environmental and genetic risk factors. An early report from China suggested that blood group A was associated with increased susceptibility and blood group O was associated with reduced susceptibility to SARS-CoV-2 infection. These reports motivated widespread interest in examining ABO blood groups as potential COVID-19 risk factors. Subsequent studies from Italy and Spain reported that blood group A was associated with an increased risk of severe COVID-19 and blood group O was associated with a reduced risk. In contrast, a large Danish study implicated disease susceptibility but not severity. However, observations from Boston and New York did not confirm any specific associations between ABO blood group and disease. The controversy raised by these contrasting reports led to this case-control study."
The researchers' objective was to independently test whether blood type is associated with SARS-CoV-2 susceptibility and COVID-19 severity. Intermountain Healthcare, a nonprofit, integrated health care system of 24 hospitals and 215 clinics in Utah, Idaho, and Nevada, generated a SARS-CoV-2 and COVID-19–specific electronic health records database. The researchers searched this database for individuals who were tested for SARS-CoV-2 between March 3 and November 2, 2020, and had a recorded blood type. For individuals who underwent multiple tests, the first test with a positive result was chosen, otherwise the first test with a negative result was used. They compared positive vs negative test results, hospitalized vs non-hospitalized patients, and intensive care unit (ICU) vs non-ICU patients. Infectivity was determined by SARS-CoV-2–specific polymerase chain reaction testing of nasal swabs or saliva samples. Analysis of variance assessed associations across ABO groups. Odds ratios (ORs) between ABO groups were assessed by logistic regression adjusted for age, sex, and Rh factor. P values were 2-sided, and statistical significance was set at P < .167 for each of the 3 primary comparisons. Statistical significance was set at P = .006 for assessment of ORs because each set underwent 9 comparisons. Data were analyzed from November 20, 2020, to February 26, 2021.
A total of 107,796 individuals (mean [SD] age, 42.0 [17.8] years; 82 875 [76.9%] women) who had been tested for SARS-CoV-2 infection were included in the study. Among individuals with COVID-19, hospitalization was associated with male sex (1165 men [50.1%] hospitalized vs 1871 men [20.5%] not hospitalized) and age (mean [SD] age among hospitalized patients, 57.0 [18.1] years vs 41.4 [14.9] years among non-hospitalized individuals). Admission to an ICU was also associated with male sex (426 men [61.8%] admitted to ICUs vs 725 men [44.8%] not admitted) and age (mean [SD] age among patients admitted to ICUs, 60.7  years vs 55.4 [18.8] years in patients not admitted). Non-White race, which included African American, American Indian or Alaskan Native, Native Hawaiian or Pacific Islander, Asian, and unknown or declined to answer, was associated with viral positivity (1592 individuals [13.9%] with positive results vs 6610 individuals [6.9%] with negative results) and hospitalization (556 patients [23.9%] hospitalized vs 1036 individuals [11.3%] not hospitalized). Blood type was not associated with disease susceptibility or severity, including viral positivity, hospitalization, or ICU admission (Table 1). Compared with type O blood, type A was not associated with increased viral positivity (OR, 0.97 [95% CI, 0.93-1.01]; P = .11), hospitalization (OR, 0.89 [95% CI, 0.80-0.99]; P = .03), or ICU admission (OR, 0.84 [95% CI, 0.69-1.02]; P = .08). Similarly, types B and AB were not associated with worse outcomes than type O. Analyses restricted to White race produced similar results.
Reference: Anderson JL, et al. Association of Sociodemographic Factors and Blood Group Type With Risk of COVID-19 in a US Population. JAMA Netw Open. 2021;4(4):e217429. doi:10.1001/jamanetworkopen.2021.7429