ABO phenotype and death in critically ill patients with COVID-19

Vitamin D status and blood group among severe COVID-19 patients

Objective

Prognosis of COVID-19 infection has been indicated to be associated with vitamin D status and ABO blood group. However, owing to discrepancies and an increased number of cases globally, the findings remain unclear. This study aimed to evaluate the association between vitamin D and ABO blood group systems in patients with severe COVID-19.

Methods

In this cross-sectional study, COVID-19 patients referred to two hospitals in the capital of Iran, Tehran, admitted to the ICU ward due to the severity of COVID-19 were evaluated. Serum vitamin D and ABO levels were evaluated in these patients. The data obtained were statistically analyzed using SPSSv24.

Results

Of 305 patients, 33.1% patients had O+ blood type, 27.8% had A+ blood type and 22.4% had B+ blood type. Vitamin D deficiency was significantly associated with a mortality rate among these patients, P<0.05. The blood group of the patients was not correlated with mortality. Thirty-seven percent of the patients in the study died because of COVID-19.

Conclusion

In our study population, mortality due to COVID-19 was significantly associated with vitamin D deficiency but not the ABO blood group. We recommend further studies in this regard that include more variable and detailed biochemical analysis.

Prevalence of ABO and RhD blood group phenotypes in the Croatian population and in patients with severe COVID-19 in Croatia

BACKGROUND

The aim of this study was to determine the distribution of ABO and RhD blood group phenotypes in the general population in the Republic of Croatia and among hospitalized patients with severe COVID-19.

MATERIALS AND METHODS

Data on ABO and RhD blood groups of all blood donors in Croatia (who donated blood during the period 2015-2020) and patients and pregnant women tested at the Croatian Institute of Transfusion Medicine during the 2-year period, 2019-2020, were obtained from the e-Delphyn blood bank information system. A total of 614,673 results were analyzed in this group. The other group consisted of 780 COVID-19 patients hospitalized with severe COVID-19. Data are presented as total number and percentages and a comparison of proportions test was performed.

RESULTS

The most frequent ABO phenotype in the general population is A (38%), followed by O (37%), B (18%) and AB (7%). RhD positive individuals accounted for 81% of the general population and RhD negative for the other 19%. Among COVID-19 patients, phenotype A was the most frequent (42%), followed by phenotypes O (32%), B (17%) and AB (9%). Thus blood group A was significantly more common among COVID-19 patients than among the general population, whereas blood group O was significantly less frequent.

DISCUSSION

This study provides the first official results of the distribution of ABO and RhD blood group phenotypes in the general population in Croatia. Moreover, this study confirms other researchers' observations about the predominance of the A blood group phenotype among COVID-19 patients.

ABO blood groups and the risk of SARS-CoV-2 infection

There is no doubt that genetic factors of the host play a role in susceptibility to infectious diseases. An association between ABO blood groups and SARS-CoV-2 infection as well as the severity of COVID-19 has been suggested relatively early during the pandemic and gained enormously high public interest. It was postulated that blood group A predisposes to a higher risk of infection as well as to a much higher risk of severe respiratory disease and that people with blood group O are less frequently and less severely affected by the disease. However, as to the severity of COVID-19, a thorough summary of the existing literature does not support these assumptions in general. Accordingly, at this time, there is no reason to suppose that knowledge of a patient's ABO phenotype should directly influence therapeutical decisions in any way. On the other hand, there are many data available supporting an association between the ABO blood groups and the risk of contracting SARS-CoV-2. To explain this association, several interactions between the virus and the host cell membrane have been proposed which will be discussed here.

Correlates of In-Hospital COVID-19 Deaths: A Competing Risks Survival Time Analysis of Retrospective Mortality Data

INTRODUCTION

Several aspects of the coronavirus disease 2019 (COVID-19) pandemic remain ambiguous, including its transmission, severity, geographic, and racial differences in mortality. These variations merit elaboration of local patterns to inform wider national policies.

METHODS

In a retrospective analysis, data of patients treated at a dedicated COVID hospital with moderate and severe illness during 8 wk of the pandemic were reviewed with attention to mortality in a competing risks framework.

RESULTS

A total of 1147 patients were hospitalized, and 312 (27.2%) died in hospital. Those who died were older (56.5 vs 47.6 y; P < 0.0001). Of these, 885 (77.2%) had tested positive on reverse transcriptase polymerase chain reaction (RT-PCR), with 219 (24.2%) deaths (incidence rate, 1.9 per 100 person-days). Median time from onset of symptoms to death was 11 days. A competing risks analysis for in-hospital death revealed an adjusted cause-specific hazard ratio of 1.4 for each decade increase in age.

CONCLUSIONS

This retrospective analysis provides broad patterns of disease presentation and mortality. Even COVID test-negative patients will receive treatment at dedicated facilities, and 33% presenting cases may die within the first 72 h, most with comorbid illness. This should be considered while planning distribution of services for effective health-care delivery.

Clinical implications of host genetic variation and susceptibility to severe or critical COVID-19

Since the start of the coronavirus disease 2019 (COVID-19) pandemic, important insights have been gained into virus biology and the host factors that modulate the human immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 displays a highly variable clinical picture that ranges from asymptomatic disease to lethal pneumonia. Apart from well-established general risk factors such as advanced age, male sex and chronic comorbidities, differences in host genetics have been shown to influence the individual predisposition to develop severe manifestations of COVID-19. These differences range from common susceptibility loci to rare genetic variants with strongly predisposing effects, or proven pathogenic variants that lead to known or novel inborn errors of immunity (IEI), which constitute a growing group of heterogeneous Mendelian disorders with increased susceptibility to infectious disease, auto-inflammation, auto-immunity, allergy or malignancies. The current genetic findings point towards a convergence of common and rare genetic variants that impact the interferon signalling pathways in patients with severe or critical COVID-19. Monogenic risk factors that impact IFN-I signalling have an expected prevalence between 1 and 5% in young, previously healthy individuals (<60 years of age) with critical COVID-19. The identification of these IEI such as X-linked TLR7 deficiency indicates a possibility for targeted genetic screening and personalized clinical management. This review aims to provide an overview of our current understanding of the host genetic factors that predispose to severe manifestations of COVID-19 and focuses on rare variants in IFN-I signalling genes and their potential clinical implications.

Race may modify the association between blood type and COVID-19 infection

This study aims to investigate the race/ethnicity-specific association between blood type and COVID-19 susceptibility during March, 2020 and December, 2021 using data from the electronic health record at the University of Chicago Medicine. The study population was stratified into four groups: non-Hispanic White, non-Hispanic Black, Hispanic, and other. Log-binomial generalized mixed model was used to estimate the relative risk (RR) and 95% confidence interval (CI). When compared to blood type O, type B was associated with positive COVID-19 test in Blacks (RR = 1.12, 95% CI: 1.02-1.23), Whites (RR = 1.28, 95% CI: 0.99-1.66), and Hispanic (RR = 1.36, 95% CI: 0.97-1.92).

ABO blood group and link to COVID-19: A comprehensive review of the reported associations and their possible underlying mechanisms

ABO blood group is long known to be an influencing factor for the susceptibility to infectious diseases, and many studies have been describing associations between ABO blood types and COVID-19 infection and severity, with conflicting findings. This narrative review aims to summarize the literature regarding associations between the ABO blood group and COVID-19. Blood type O is mostly associated with lower rates of SARS-CoV-2 infection, while blood type A is frequently described as a risk factor. Although results regarding the risk of severe outcomes are more variable, blood type A is the most associated with COVID-19 severity and mortality, while many studies describe O blood type as a protective factor for the disease progression. Furthermore, genetic associations with both the risk of infection and disease severity have been reported for the ABO locus. Some underlying mechanisms have been hypothesized to explain the reported associations, with incipient experimental data. Three major hypotheses emerge: SARS-CoV-2 could carry ABO(H)-like structures in its envelope glycoproteins and would be asymmetrically transmitted due to a protective effect of the ABO antibodies, ABH antigens could facilitate SARS-CoV-2 interaction with the host’ cells, and the association of non-O blood types with higher risks of thromboembolic events could confer COVID-19 patients with blood type O a lower risk of severe outcomes. The hypothesized mechanisms would affect distinct aspects of the COVID-19 natural history, with distinct potential implications to the disease transmission and its management.

SARS-CoV-2 and mutation RT-qPCR test positivity correlation with ABO and Rh blood types

Studies show that there may be a relationship between ABO blood type and SARS‐CoV‐2 transmission. It was aimed to determine by investigating the blood type of patients whose one‐step reverse transcription and real‐time polymerase chain reaction (RT‐qPCR) test were positive for SARS‐CoV‐2. ABO and Rh blood types of individuals whose RT‐qPCR test was positive for SARS‐CoV‐2 were examined and an evaluation was made to identify whether there was a relationship between them or not. The blood type data of 44.928 SARS‐CoV‐2 positive RT‐qPCR test results have been obtained. 17.656 (39.29%) were delta, 8048 (17.91%) were alpha, 800 (1.78%) were beta, and 3000 (6.67%) were omicrons while 15.424 (34.33%) SARS‐CoV‐2 positive mutation was found to be negative. Our study suggests that O and Rh (−) blood types may provide protection against delta, AB and Rh (+) blood types may hinder omicron infection while A and Rh (+) blood types may be more vulnerable to alpha and delta while B and Rh (+) are more sensitive to beta mutation. The molecular mechanism underlying the relationship between blood types and SARS‐CoV‐2 infection needs further molecular studies and multi‐centered studies.

Relationship between ABO Blood Group Distribution and COVID-19 Infection in Patients Admitted to the ICU: A Multicenter Observational Spanish Study

Since the beginning of the COVID-19 pandemic in December 2019, a relationship between the ABO blood group type and the novel coronavirus SARS-CoV-2, the etiological agent of COVID-19, has been reported, noting that individuals with the O blood group are the least likely to be infected. Spain is one of the most badly affected countries worldwide, with high rates of patients diagnosed, hospitalized, and deceased due to COVID-19 infection. The present study aimed to analyze the possible relationship of ABO in COVID-19 patients hospitalized in different Spanish centers during the first wave of the COVID-19 pandemic, for which the ABO group was available. Physicians from the transfusion services of different Spanish hospitals, who have developed a multicenter retrospective observational study, were invited to participate voluntarily in the research and 12,115 patients with COVID-19 infection were admitted to the nine participating hospitals. The blood group was known in 1399 cases (11.5%), of which 365 (26.1%) were admitted to the ICU. Regarding the distribution of ABO blood groups, a significant increase in the non-O blood groups and reduction for the O blood group was observed in patients hospitalized due to COVID-19, compared to the reference general population. Among the patients admitted to the ICU, after multivariate analysis, adjusted for the rest of the confounding variables, patients with the O blood group presented a significantly lower risk for admission to the ICU. We conclude that an association was observed between patients with the O blood group and their lower susceptibility to SARS-CoV-2 infection, both for those admitted to the hospitalization ward and for those who required admission to the ICU.

Asociación del grupo sanguíneo ABO con complicaciones en covid-19 : revisión sistemática y meta-análisis

Introducción: los grupos sanguíneos ABO han sido utilizados como marcadores de desenlace en diferentes enfermedades, otorgando al grupo O un factor protector y al A uno de riesgo. Durante el brote de SARS CoV-1 se planteó la posible relación entre riesgo de infección y tipo sanguíneo; se presume que en la pandemia por COVID-19 exista una relación entre determinados desenlaces y los grupos ABO. Objetivo:  determinar la asociación entre los diferentes grupos sanguíneos y los desenlaces de mortalidad, ingreso a cuidados intensivos y requerimiento de intubación orotraqueal (IOT) en población con infección por COVID-19. Materiales y métodos: revisión sistemática y metanálisis entre enero 2020 y marzo 2021 en las bases de datos MEDLINE, EMBASE, SCOPUS, Latindex y LILACS, identificando los desenlaces mencionados en pacientes con COVID-19. Resultados: se incluyeron 16 estudios, la mayoría retrospectivos multicéntricos. Se evidenció que pacientes con grupo sanguíneo A tienen mayor riesgo de mortalidad (OR 1.08 ;1.01-0.17), frente al ingreso a UCI no hubo diferencia estadística significativa entre los grupos sanguíneos. Se encontró que el AB representa un factor de riesgo para intubación orotraqueal (OR 1.42 IC95% 1.02-1.96), en tanto que el A demostró proteger contra este desenlace (OR 0.84 IC95%0.73-0.97). Conclusiones: hay evidencia sobre la relación entre el grupo sanguíneo y los desenlaces, asociada con la infección por SARS-CoV-2. Se requieren estudios prospectivos que evalúen grupo sanguíneo, RH y desenlaces específicos.

Persistent Overactive Cytotoxic Immune Response in a Spanish Cohort of Individuals With Long-COVID: Identification of Diagnostic Biomarkers

Long-COVID is a new emerging syndrome worldwide that is characterized by the persistence of unresolved signs and symptoms of COVID-19 more than 4 weeks after the infection and even after more than 12 weeks. The underlying mechanisms for Long-COVID are still undefined, but a sustained inflammatory response caused by the persistence of SARS-CoV-2 in organ and tissue sanctuaries or resemblance with an autoimmune disease are within the most considered hypotheses. In this study, we analyzed the usefulness of several demographic, clinical, and immunological parameters as diagnostic biomarkers of Long-COVID in one cohort of Spanish individuals who presented signs and symptoms of this syndrome after 49 weeks post-infection, in comparison with individuals who recovered completely in the first 12 weeks after the infection. We determined that individuals with Long-COVID showed significantly increased levels of functional memory cells with high antiviral cytotoxic activity such as CD8+ TEMRA cells, CD8±TCRγδ+ cells, and NK cells with CD56+CD57+NKG2C+ phenotype. The persistence of these long-lasting cytotoxic populations was supported by enhanced levels of CD4+ Tregs and the expression of the exhaustion marker PD-1 on the surface of CD3+ T lymphocytes. With the use of these immune parameters and significant clinical features such as lethargy, pleuritic chest pain, and dermatological injuries, as well as demographic factors such as female gender and O+ blood type, a Random Forest algorithm predicted the assignment of the participants in the Long-COVID group with 100% accuracy. The definition of the most accurate diagnostic biomarkers could be helpful to detect the development of Long-COVID and to improve the clinical management of these patients.

Does the Serum Concentration of Angiotensin II Type 1 Receptor Have an Effect on the Severity of COVID-19? A Prospective Preliminary Observational Study among Healthcare Professionals

SARS-CoV-2 is a virus that causes severe respiratory distress syndrome. The pathophysiology of COVID-19 is related to the renin-angiotensin system (RAS). SARS-CoV-2, a vector of COVID-19, uses angiotensin-converting enzyme 2 (ACE-2), which is highly expressed in human lung tissue, nasal cavity, and oral mucosa, to gain access into human cells. After entering the cell, SARS-CoV-2 inhibits ACE-2, thus favouring the ACE/Ang II/angiotensin II type 1 receptor (AT1R) axis, which plays a role in the development of acute lung injury (ALI). This study aimed to analyse the influence of angiotensin 1 receptor (AT1R) levels in the serum on the course of the severity of symptoms in healthcare professionals who had a SARS-CoV-2 infection. This prospective observational study was conducted on a group of 82 participants. The study group included physicians and nurses who had a COVID-19 infection confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) test for SARS-CoV-2. The control group consisted of healthy medical professionals who had not had a SARS-CoV-2 infection or who had no symptoms of COVID-19 and who tested negative for SARS-CoV-2 on the day of examination. We analysed the correlation between AT1R concentration and the severity of COVID-19, as well as with sex, age, blood group, and comorbidities. There were no statistically significant differences in the mean values of AT1R concentration in the recovered individuals and the non-COVID-19 subjects (3.29 vs. 3.76 ng/mL; p = 0.32). The ROC curve for the AT1R assay showed an optimal cut-off point of 1.33 (AUC = 0.44; 95% CI = 0.32-0.57; p = 0.37). There was also no correlation between AT1R concentration and the severity of symptoms associated with COVID-19. Blood type analysis showed statistically significantly lower levels of AT1R in COVID-19-recovered participants with blood group A than in those with blood group O. In conclusion, AT1R concentration does not affect the severity of symptoms associated with COVID-19 among healthcare professionals.

Persistence of Naturally Acquired and Functional SARS-CoV-2 Antibodies in Blood Donors One Year after Infection

The developmental course of antibodies produced after a SARS-CoV-2 infection has been insufficiently investigated so far. Therefore, the aim of this study was to investigate the dynamics of SARS-CoV-2 antibody levels against the viral nucleocapsid- and spike-protein among Austrian blood donors as a representative group of a supposedly healthy population within the first year after a SARS-CoV-2 infection. The impact of age, sex, vaccination status, AB0-blood group and awareness about the infection was evaluated. Our study shows that the level of anti-N antibodies is declining, while anti-S antibody levels remain stable. Antibodies detected were functional in vitro. Age, sex and blood group do not influence antibody dynamics. However, blood group AB shows significantly lower antibody levels and in vitro functionality compared to other blood groups. Our data reveal that one out of five individuals was not aware of a previous SARS-CoV-2 infection and that the disease course neither affects the level of antibody production nor the in vitro functionality. We also found that 14% of participants show persisting COVID-19-related symptoms for up to nine months. Our results provide valuable insights into the dynamics of the immune response after a SARS-CoV-2 infection in a representative cohort of adult blood donors in Central Europe.

In Planta Production of the Receptor-Binding Domain From SARS-CoV-2 With Human Blood Group A Glycan Structures

Glycosylation of viral envelope proteins is important for infectivity and immune evasion. The SARS-CoV-2 spike protein is heavily glycosylated and host-derived glycan modifications contribute to the formation of specific immunogenic epitopes, enhance the virus-cell interaction or affect virus transmission. On recombinant viral antigens used as subunit vaccines or for serological assays, distinct glycan structures may enhance the immunogenicity and are recognized by naturally occurring antibodies in human sera. Here, we performed an in vivo glycoengineering approach to produce recombinant variants of the SARS-CoV-2 receptor-binding domain (RBD) with blood group antigens in Nicotiana benthamiana plants. SARS-CoV-2 RBD and human glycosyltransferases for the blood group ABH antigen formation were transiently co-expressed in N. benthamiana leaves. Recombinant RBD was purified and the formation of complex N-glycans carrying blood group A antigens was shown by immunoblotting and MS analysis. Binding to the cellular ACE2 receptor and the conformation-dependent CR3022 antibody showed that the RBD glycosylation variants carrying blood group antigens were functional. Analysis of sera from RBD-positive and RBD-negative individuals revealed further that non-infected RBD-negative blood group O individuals have antibodies that strongly bind to RBD modified with blood group A antigen structures. The binding of IgGs derived from sera of non-infected RBD-negative blood group O individuals to blood group A antigens on SARS-CoV-2 RBD suggests that these antibodies could provide some degree of protection from virus infection.

The relationship between blood groups and risk of infection with SARS-CoV-2 or development of severe outcomes: A review

The outbreak of coronavirus disease 2019 (COVID‐19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is considered a global catastrophe that has overwhelmed health care systems. Since initiation of the pandemic, identification of characteristics that might influence risk of infection and poor disease outcomes have been of paramount interest. Blood group phenotypes are genetically inherited characteristics whose association with certain infectious diseases have long been debated. The aim of this review is to identify whether a certain type of blood group may influence an individual’s susceptibility to SARS‐CoV‐2 infection and developing severe outcomes. Our review shows that blood group O protects individuals against SARS‐CoV‐2, whereas blood group A predisposes them to being infected. Although the association between blood groups and outcomes of COVID‐19 is not consistent, it is speculated that non‐O blood group carriers with COVID‐19 are at higher risk of developing severe outcomes in comparison to O blood group. The interaction between blood groups and SARS‐CoV‐2 infection is hypothesized to be as result of natural antibodies against blood group antigens that may act as a part of innate immune response to neutralize viral particles. Alternatively, blood group antigens could serve as additional receptors for the virus and individuals who are capable of expressing these antigens on epithelial cells, which are known as secretors, would then have a high propensity to be affected by SARS‐CoV‐2.

Susceptibility of ABO blood group to COVID-19 infections: clinico-hematological, radiological, and complications analysis

In the wake of the COVID-19 pandemic, research indicates that the COVID-19 disease susceptibility varies among individuals depending on their ABO blood groups. Researchers globally commenced investigating potential methods to stratify cases according to prognosis depending on several clinical parameters. Since there is evidence of a link between ABO blood groups and disease susceptibility, it could be argued that there is a link between blood groups and disease manifestation and progression. The current study investigates whether clinical manifestation, laboratory, and imaging findings vary among ABO blood groups of hospitalized confirmed COVID-19 patients.This retrospective cohort study was conducted between March 1, 2020 and March 31, 2021 in King Faisal Specialist Hospital and Research Centre Riyadh and Jeddah, Saudi Arabia. Demographic information, clinical information, laboratory findings, and imaging investigations were extracted from the data warehouse for all confirmed COVID-19 patients.A total of 285 admitted patients were included in the study. Of these, 81 (28.4%) were blood group A, 43 (15.1%) were blood group B, 11 (3.9%) were blood group AB, and 150 (52.6%) were blood group O. This was almost consistent with the distribution of blood groups among the Saudi Arabia community. The majority of the study participants (79.6% [n = 227]) were asymptomatic. The upper respiratory tract infection (P = .014) and shortness of breath showed statistically significant differences between the ABO blood group (P = .009). Moreover, the incidence of the symptoms was highly observed in blood group O followed by A then B except for pharyngeal exudate observed in blood group A. The one-way ANOVA test indicated that among the studied hematological parameters, glucose (P = .004), absolute lymphocyte count (P = .001), and IgA (P = .036) showed statistically significant differences between the means of the ABO blood group. The differences in both X-ray and computed tomography scan findings were statistically nonsignificant among the ABO age group. Only 86 (30.3%) patients were admitted to an intensive care unit, and the majority of them were blood groups O 28.7% (n = 43) and A 37.0% (n = 30). However, the differences in complications' outcomes were statistically nonsignificant among the ABO age group.ABO blood groups among hospitalized COVID-19 patients are not associated with clinical, hematological, radiological, and complications abnormality.

Demographic and Clinical Factors Associated with Reactivity of Anti-SARS-CoV-2 Antibodies in Serbian Convalescent Plasma Donors

Passive immunotherapy with convalescent COVID-19 plasma (CCP) is used as a therapeutic procedure in many countries, including Serbia. In this study, we analyzed the association between demographic factors, COVID-19 severity and the reactivity of anti-SARS-CoV-2 antibodies (Abs) in Serbian CCP donors. Individuals (n = 468) recovered from confirmed SARS-CoV-2 infection, and who were willing to donate their plasma for passive immunization of COVID-19 patients were enrolled in the study. Plasma samples were tested for the presence of IgG reactive to SARS-CoV-2 spike glycoprotein (S1) and nucleocapsid antigens. Individuals were characterized according to age, gender, comorbidities, COVID-19 severity, ABO blood type and RhD factor. Total of 420 candidates (420/468; 89.74%) reached the levels of anti-SARS-CoV-2 IgG that qualified them for inclusion in CCP donation program. Further statistical analysis showed that male individuals (p = 0.034), older age groups (p < 0.001), existence of hypertension (p = 0.008), and severe COVID-19 (p = 0.000) are linked with higher levels of anti-SARS-CoV-2 Abs. These findings will guide the selection of CCP donors in Serbia. Further studies need to be conducted to assess the neutralization potency and clinical efficiency of CCP collected from Serbian donors with high anti-SARS-CoV-2 IgG reactivity.

Generation and Export of Red Blood Cell ATP in Health and Disease

Metabolic homeostasis in animals depends critically on evolved mechanisms by which red blood cell (RBC) hemoglobin (Hb) senses oxygen (O₂) need and responds accordingly. The entwined regulation of ATP production and antioxidant systems within the RBC also exploits Hb-based O₂-sensitivity to respond to various physiologic and pathophysiologic stresses. O₂ offloading, for example, promotes glycolysis in order to generate both 2,3-DPG (a negative allosteric effector of Hb O₂ binding) and ATP. Alternatively, generation of the nicotinamide adenine dinucleotide phosphate (NADPH) critical for reducing systems is favored under the oxidizing conditions of O₂ abundance. Dynamic control of ATP not only ensures the functional activity of ion pumps and cellular flexibility, but also contributes to the availability of vasoregulatory ATP that can be exported when necessary, for example in hypoxia or upon RBC deformation in microvessels. RBC ATP export in response to hypoxia or deformation dilates blood vessels in order to promote efficient O₂ delivery. The ability of RBCs to adapt to the metabolic environment via differential control of these metabolites is impaired in the face of enzymopathies [pyruvate kinase deficiency; glucose-6-phosphate dehydrogenase (G6PD) deficiency], blood banking, diabetes mellitus, COVID-19 or sepsis, and sickle cell disease. The emerging availability of therapies capable of augmenting RBC ATP, including newly established uses of allosteric effectors and metabolite-specific additive solutions for RBC transfusates, raises the prospect of clinical interventions to optimize or correct RBC function via these metabolite delivery mechanisms.

ABO and Rhesus Blood Groups in Acute Puumala Hantavirus Infection

Puumala hantavirus (PUUV) causes hemorrhagic fever with renal syndrome. We aimed to evaluate whether ABO and rhesus blood groups associate with the susceptibility or the severity of PUUV infection. We analyzed blood groups in 289 adult patients treated in Tampere University hospital due to PUUV infection during the years 1982–2017. Patients’ blood group distribution was compared to that of healthy, voluntary blood donors living in the Tampere University Hospital responsibility area (n = 21,833). The severity of PUUV infection, as judged by the severity of acute kidney injury (AKI), thrombocytopenia, inflammation, capillary leakage, and the length of hospital care, was analyzed across the groups. The ABO and rhesus blood group distributions did not differ between the patients and blood donors. Patients with non-O blood groups had lower systolic blood pressure compared to patients with blood group O, but there was no difference in other markers of capillary leakage or in the severity of AKI. Minor deviations in the number of platelets and leukocytes were detected between the O and non-O blood groups. To conclude, patients with blood group O may be less susceptible to hypotension, but otherwise blood groups have no major influences on disease susceptibility or severity during acute PUUV infection.

Relationship between blood type and outcomes following COVID-19 infection

Since the onset of the COVID-19 pandemic, a concentrated research effort has been undertaken to elucidate risk factors underlying viral infection, severe illness, and death. Recent studies have investigated the association between blood type and COVID-19 infection. This article aims to comprehensively review current literature and better understand the impact of blood type on viral susceptibility and outcomes.

Lewis and ABO histo-blood types and the secretor status of patients hospitalized with COVID-19 implicate a role for ABO antibodies in susceptibility to infection with SARS-CoV-2

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) targets the respiratory and gastric epithelium, causing coronavirus disease 2019 (COVID-19). Tissue antigen expression variations influence host susceptibility to many infections. This study aimed to investigate the closely linked Lewis (FUT3) and ABO histo-blood types, including secretor (FUT2) status, to infections with SARS-CoV-2 and the corresponding severity of COVID-19.

STUDY DESIGN AND METHODS

Patients (Caucasians, n = 338) were genotyped for ABO, FUT3, and FUT2, and compared to a reference population of blood donors (n = 250,298). The association between blood types and severity of COVID-19 was addressed by dividing patients into four categories: hospitalized individuals in general wards, patients admitted to the intensive care unit with and without intubation, and deceased patients. Comorbidities were considered in subsequent analyses.

RESULTS

Patients with blood type Lewis (a-b-) or O were significantly less likely to be hospitalized (odds ratio [OR] 0.669, confidence interval [CI] 0.446-0.971, OR 0.710, CI 0.556-0.900, respectively), while type AB was significantly more prevalent in the patient cohort (OR 1.519, CI 1.014-2.203). The proportions of secretors/nonsecretors, and Lewis a+ or Lewis b+ types were consistent between patients and controls. The analyzed blood groups were not associated with the clinical outcome as defined.

DISCUSSION

Blood types Lewis (a-b-) and O were found to be protective factors, whereas the group AB is suggested to be a risk factor for COVID-19. The antigens investigated may not be prognostic for disease severity, but a role for ABO isoagglutinins in SARS-CoV-2 infections is strongly suggested.

ABO phenotype and clinical correlates of COVID-19 severity in hospitalized patients

AIM

This study investigates the association between ABO blood phenotype and COVID-19 severity, measured by intensive care unit admission, need for intubation, hospitalization length and death. It further explores clinical predictors of COVID-19 severity within a primarily Hispanic demographic in San Diego County.

MATERIALS & METHODS

We retrospectively reviewed 942 total patients, 473 with available blood type, hospitalized at five Scripps Health hospitals with COVID-19.

RESULTS

No significant association was found between ABO phenotype and COVID-19 severity on multivariate analysis, while a diagnosis of anemia and male sex was associated with all severity outcomes on exploratory analysis.

CONCLUSION

Our results provide relevant clinical correlates of COVID-19 severity and help better elucidate the association between ABO phenotype and COVID-19.

Association between blood groups and COVID-19 outcome in Iranian patients

Aim: Many factors have been speculated to explain the COVID-19 complex clinical phenotype. Due to the inconsistent data published on blood groups and COVID-19, we conducted a study on Iranian patients to further assess this association. Materials & methods: This retrospective study was conducted on data collected from confirmed COVID-19 hospitalized patients during March and December 2020 in a referral hospital for COVID-19, 5 Azar Hospital, Gorgan, north of Iran. A total of 1554 confirmed COVID-19 cases were enrolled in the study with blood group (ABO and Rh), demographic, and clinical data available. Results: Of 1554 patients, 1267 and 287 cases had recovered and deceased (due to COVID-19) outcomes, respectively. Most of the cases had O+ (29.6%), the least number had AB- (0.5%), and most of the deceased cases had O+ blood types (31.4%). Logistic regression analysis revealed that groups A- and B- had higher and groups B+, AB+, O+ and O- had lower odds of death than the A+ group. Conclusion: This study indicates that blood types may be related to the clinical outcome of COVID-19. Further studies with a large cohort for multiple people are required to validate this association.

HLA-A homozygosis is associated with susceptibility to COVID-19

The purpose of this single center retrospective study was to investigate the relationship between HLA and ABO polymorphisms and COVID-19 susceptibility and severity in kidney transplant recipients. It included 720 recipients who had COVID-19 and 1680 controls composed by recipients in follow-up who did not contact the transplantation center for COVID-19 symptoms, up to the moment of their inclusion in the study. HLA-A, -B, and -DRB1 allele groups and ABO frequencies were compared between recipients with COVID-19 (all cases, or separately mild/moderate and severe disease) and controls. The HLA association study was conducted in two case-control series and only associations that showed a p-value <0.05 in both series were considered. No HLA association regarding COVID-19 occurrence or severity met this criterion. Homozygosity at HLA-A locus was associated with COVID-19 susceptibility (odds ratio 1.4) but not severity. Blood groups A and O were associated with susceptibility and resistance to COVID-19, respectively. COVID-19 severity was associated only with older age and cardiac disease, in a multivariate analysis. We conclude that an influence of HLA on COVID-19 susceptibility is supported by the association with homozygosity at HLA-A locus but that there is no evidence for a role of any particular HLA-A, -B, or -DRB1 polymorphism. Thus, we suggest that what matters is the overall capability of an individual's HLA molecules to present SARS-CoV-2 peptides to T cells, a factor that might have a great influence on the breadth of the immune response.

Does ABO Blood Groups Affect Outcomes in Hospitalized COVID-19 Patients?

Background

Blood group type A has been associated with increased susceptibility for coronavirus disease 2019 (COVID-19) infection when compared to group O. The aim of our study was to examine outcomes in hospitalized COVID-19 patients among blood groups A and O.

Methods

This is an observational study. Kruskal-Wallis and Chi-square tests were used to compare continuous and categorical variables. Multivariable logistic regression models were used to examine association of blood groups with rates of mortality and severity of disease. All adult patients (> 18 years) admitted with COVID-19 infection between March 1, 2020 and March 10, 2021 at a large community hospital in Northeast Georgia were included. We compared mortality, severity of disease (use of mechanical ventilation, vasopressor, and acute renal failure), rates of venous thromboembolism and inflammatory markers between the blood groups. We used multivariable logistic regression model to adjust for demographical and clinical characteristics, use of COVID-19 medications and severity.

Results

A total of 3,563 of 5,204 admitted patients had information on blood groups. Of these, 1,301 (36.5%) were group A, 377 (10.6 %) were group B, 133 (3.7%) were group AB and 1,752 (49.2%) were group O. On adjusted analysis, there were no significant differences in rates of intensive care unit (ICU) admissions, mechanical ventilation, vasopressors, acute renal failure, venous thromboembolism and readmission rate between the blood groups A and O. In-hospital mortality was also not statistically different among the blood groups A and O (17.5% vs. 20.1%; P = 0.07). On adjusted analysis, in-hospital mortality was not lower in blood groups O (odds ratio (OR): 1.06; 95% confidence interval (CI): 0.80 - 1.40, P = 0.70).

Conclusions

Once hospitalized with COVID-19 infection, blood groups A and O are not associated with increased severity or in-hospital mortality.

Systematic review and meta-analysis of the susceptibility of ABO blood group to COVID-19 infection

Background

Numerous studies investigate the association between the ABO blood groups and the occurrence of COVID-19 infection; discordant findings were reported. Therefore, the purpose of this meta-analysis was to evaluate the existing evidence on the susceptibility of the ABO blood group to COVID-19 infection.

Methods

Systematically searched published articles in PubMed, Google Scholar, Scopus, and EMBASE between 1 st January 2020 and 21 st March 2021. After quality control and the exclusion of irrelevant studies, 16 studies were included in the final analysis.

Results

Although the random-effect meta-analysis revealed a large heterogeneity among studies, I 2 = 99.197 %. The pooled event rates and (95 % CIs) for A, O, B, and AB blood group were 0.459 (95 %CI: 0.358–0.441), 0.342 (95 %CI: 0.298–0.374), 0.180 (95 %CI: 0.150–0.214), and 0.076 (95 %CI: 0.055–0.127), respectively. These results indicated that the COVID-19 infection rate was higher in persons with blood group A > O > B > AB. Overall, the ABO blood group's vulnerability to COVID-19 infection was statistically significant (pooled p -value<0.001).

Conclusion

This meta-analysis offers a further indication of blood group A individuals' vulnerability to COVID-19 infection, and blood type AB are linked to a lower risk of COVID-19 infection.

SARS-CoV-2 Infection Susceptibility of Pregnant Patients at Term Regarding ABO and Rh Blood Groups: A Cohort Study

Background and Objectives: The susceptibility of pregnant patients at term to SARS-CoV-2 infection regarding the ABO and Rh blood group polymorphism was analyzed in this study. Materials and Methods: In this prospective study, 457 patients admitted for delivery at term in our hospital, between 1 April 2020 and 31 December 2020 were studied. There were 46 positive and 411 SARS-CoV-2 negative patients. Their values for RT-PCR, ABO, and Rh blood group analyses, which were determined upon admittance, were studied. Results: A slightly higher percentage of infected pregnant patients at term belonged to the A blood group compared with the percentage belonging to the other blood groups; this was also true for the healthy control group. For the Rh-negative pregnant patients at term, the odds of being infected with SARS-CoV-2 was OR = 1.22 compared with Rh-positive patients where OR = 1. In our study, the highest risk was found among BIII Rh-negative pregnant patients at term (OR = 3). None of the above differences were statistically significant. Conclusions: No significant difference was found between the percentage of ABO or Rh blood groups in SARS-CoV-2 positive patients when compared with SARS-CoV-2 negative patients (p = 0.562).

Does blood type affect the COVID-19 infection pattern?

Among the many aspects that characterize the COVID-19 pandemic, two seem particularly challenging to understand: i) the great geographical differences in the degree of virus contagiousness and lethality that were found in the different phases of the epidemic progression, and, ii) the potential role of the infected people's blood type in both the virus infectivity and the progression of the disease. A recent hypothesis could shed some light on both aspects. Specifically, it has been proposed that, in the subject-to-subject transfer, SARS-CoV-2 conserves on its capsid the erythrocytes' antigens of the source subject. Thus these conserved antigens can potentially cause an immune reaction in a receiving subject that has previously acquired specific antibodies for the source subject antigens. This hypothesis implies a blood type-dependent infection rate. The strong geographical dependence of the blood type distribution could be, therefore, one of the factors at the origin of the observed heterogeneity in the epidemics spread. Here, we present an epidemiological deterministic model where the infection rules based on blood types are taken into account, and we compare our model outcomes with the exiting worldwide infection progression data. We found an overall good agreement, which strengthens the hypothesis that blood types do play a role in the COVID-19 infection.

ABO blood group and COVID-19: an updated systematic literature review and meta-analysis

BACKGROUND

Following the first reports in the literature, the association between the ABO blood group and SARS-CoV-2 infection has been investigated by a number of studies, although with varying results. The main object of this systematic review was to assess the relationship between the ABO blood group and the occurrence and severity of COVID-19.

MATERIALS AND METHODS

A systematic literature search using appropriate MeSH terms was performed through Medline and PubMed. The outcomes considered were the prevalence of the blood group O vs non-O types in SARS-CoV-2 infected and non-infected subjects, and the severity of SARS-CoV-2 infection according to ABO group. The methodological quality of the studies included in the analysis was assessed with the Newcastle-Ottawa Scale, and the overall quality of the available evidence using the GRADE system. Benchmarks used to evaluate the effect size were odd ratios (ORs) for case control studies and risk ratios (RRs) for cohort studies.

RESULTS

Twenty-one studies were included in the analysis. Overall, individuals with group O had a lower infection rate compared to individuals of non-O group (OR: 0.81; 95% CI: 0.75, 0.86). However, the difference in the effect size was significantly lower in cohort studies compared to case control studies. No evidence was found indicating an effect of the O type on the disease severity in the infected patients.

DISCUSSION

We have found low/very low evidence that group O individuals are less susceptible to SARS-CoV-2 infection compared to those in the non-O group. No evidence was found indicating an effect of the O type on disease severity in SARS-CoV-2 infection.

The impact of ABO blood groups on clinical outcomes and susceptibility to COVID-19: A retrospective study in an unselected population

BACKGROUND

ABO blood groups have been linked to susceptibility to infection with certain microorganisms, including coronaviruses. We examined the relationship between blood group and clinical outcomes in individuals infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and compared their blood group distribution with the general population.

METHODS

At the inception of the pandemic, all individuals testing positive for SARS-CoV-2 in Kuwait were admitted to one designated coronavirus disease 2019 (COVID-19) hospital and enrolled in a prospective registry. Patients admitted from February 24 to May 27, 2020, were stratified according to blood group. As a control, blood groups of 3,730,027 anonymized individuals representing almost Kuwait's entire population were obtained from a national database.

RESULTS

Of 3305 SARS-CoV-2-positive patients, 37.1%, 25.5%, 28.9%, and 8.5% were groups O, A, B, and AB, respectively. Univariate analysis revealed no significant differences in severe clinical outcomes or death among the blood groups. However, multivariable analysis demonstrated that group A individuals had higher odds of developing pneumonia compared with non-group A (adjusted odds ratio 1.32, 95% confidence interval 1.02-1.72, p < .036). Compared with the general population, the COVID-19 cohort had a lower frequency of group O, equivalent frequency of A, and higher frequency of B and AB. No significant difference in the RhD group was found.

CONCLUSION

This study supports potential involvement of the ABO blood group system in predisposing to infection with SARS-CoV-2 in an unselected population. Examination of the mechanistic link between blood group and COVID-19 and its implications on controlling the current pandemic is warranted.

Blood group type A secretors are associated with a higher risk of COVID-19 cardiovascular disease complications

The SARS-CoV-2 virus causes COVID-19, an infection capable of causing severe disease and death but which can also be asymptomatic or oligosymptomatic. We investigated whether ABO blood group or secretor status was associated with COVID-19 severity. We investigated secretor status because expression of ABO glycans on secreted proteins and non-erythroid cells are controlled by a fucosyltransferase (FUT2), and inactivating FUT2 mutations result in a non-secretor phenotype which protects against some viral infections. Data combined from healthcare records and our own laboratory tests (n = 275) of hospitalized SARS-CoV-2 polymerase chain reaction positive patients confirmed higher than expected numbers of blood group A individuals compared to O (RR = 1.24, CI 95% [1.05, 1.47], p = 0.0111). There was also a significant association between group A and COVID-19-related cardiovascular complications (RR = 2.56, CI 95% [1.43, 4.55], p = 0.0011) which is independent of gender. Molecular analysis revealed that group A non-secretors are significantly less likely to be hospitalized than secretors. Testing of convalescent plasma donors, among whom the majority displayed COVID-19 symptoms and only a small minority required hospitalization, group A non-secretors were slightly over-represented. Our findings showed that group A non-secretors are not resistant to infection by SARS-CoV-2, but are more likely to experience a less severe form of associated disease.

ABO blood type association with SARS-CoV-2 infection mortality: A single-center population in New York City

Background

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has a variable clinical course with significant mortality. Early reports suggested higher rates of SARS‐CoV‐2 infection in patients with type A blood and enrichment of type A individuals among COVID‐19 mortalities.

Study Design and Methods

The study includes all patients hospitalized or with an emergency department (ED) visit who were tested for SARS‐CoV‐2 between March 10, 2020 and June 8, 2020 and had a positive test result by nucleic acid test (NAT) performed on a nasopharyngeal swab specimen. A total of 4968 patients met the study inclusion criteria, with a subsequent 23.1% (n = 1146/4968) all‐cause mortality rate in the study cohort. To estimate overall risk by ABO type and account for the competing risks of in‐hospital mortality and discharge, we calculated the cumulative incidence function (CIF) for each event. Cause‐specific hazard ratios (csHRs) for in‐hospital mortality and discharge were analyzed using multivariable Cox proportional hazards models.

Results

Type A blood was associated with the increased cause‐specific hazard of death among COVID‐19 patients compared to type O (HR = 1.17, 1.02–1.33, p = .02) and type B (HR = 1.32,1.10–1.58, p = .003).

Conclusions

Our study shows that ABO histo‐blood group type is associated with the risk of in‐hospital death in COVID‐19 patients, warranting additional inquiry. Elucidating the mechanism behind this association may reveal insights into the susceptibility and/or immunity to SARS‐CoV‐2.

Covid-19 and blood groups: ABO antibody levels may also matter

BACKGROUND

Susceptibility to Covid-19 has been found to be associated with the ABO blood group, with O type individuals being at a lower risk. However, the underlying mechanism has not been elucidated. Here, we aimed to test the hypothesis that Covid-19 patients might have lower levels of ABO antibodies than non-infected individuals as they could offer some degree of protection.

METHODS

After showing that the viral spike protein harbors the ABO glycan epitopes when produced by cells expressing the relevant glycosyltransferases, like upper respiratory tract epithelial cells, we enrolled 290 patients with Covid-19 and 276 asymptomatic controls to compare their levels of natural ABO blood group antibodies.

RESULTS

We found significantly lower IgM anti-A + anti-B agglutination scores in blood group O patients (76.93 vs 88.29, P-value = 0.034) and lower levels of anti-B (24.93 vs 30.40, P-value = 0.028) and anti-A antibodies (28.56 vs 36.50, P-value = 0.048) in blood group A and blood group B patients, respectively, compared to controls.

CONCLUSION

In this study, we showed that ABO antibody levels are significantly lower in Covid-19 patients compared to controls. These findings could indicate that patients with low levels of ABO antibodies are at higher risk of being infected.

Retrospective analysis of 426 donors of a convalescent collective after mild COVID-19

BACKGROUND

The novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the world. The aim of our study was to characterize mild courses and to determine the antibody status for these patients.

METHODS

We initiated an appeal for convalescent plasma donations. 615 people contacted us, and we ultimately included 426 in our analyses, in whom it was possible to assume COVID-19 based on detection of specific SARS-CoV-2 antibodies or virus detection during the disease using RT-PCR.

RESULTS

The median duration of the disease was 12 days and the most common symptoms were fatigue, cough and olfactory and gustatory dysfunction. Anti-SARS-CoV-2 IgG was detected in 82.4% of the persons and IgA antibodies were found in 73.9%. In 10.8%, no antibodies were detectable despite a positive RT-PCR result during the disease. Nevertheless, of 24 persons with asymptomatic courses of COVID-19, antibodies against SARS-CoV-2 could be detected in 23 (96%). Furthermore, there was a correlation between the duration of the disease and the detection of IgG antibodies. In addition, a correlation between the determined IgG antibodies and neutralizing antibodies was shown.

CONCLUSION

In this study, we were able to describe mild COVID-19 courses and determine antibody statuses for them. It could be shown that, despite SARS-CoV-2 detection during the disease, not all individuals developed antibodies or their level of antibodies had dropped below the detection limit shortly after the end of the disease. The extent to which immunity to re-infection is given in persons with undetectable antibodies (IgG, IgA) needs to be investigated in future studies.

The association of ABO blood type with the risk and severity of COVID-19 infection

BACKGROUND

There is conflicting data in the literature about the association of ABO blood type and susceptibility to COVID-19 infection. Moreover, very few studies have examined the effect of blood type on severity of COVID-19 infection.

METHODS

This was a retrospective, single-center analysis of adult patients with COVID-19 infection who were hospitalized between March 8^th to July 31^st, 2020 at a regional tertiary care hospital. All patients who were hospitalized with a diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection and had a documented ABO blood type were enrolled in this analysis. Aims of this study were to examine the prevalence of ABO blood types in patients with COVID-19 infection and to determine the frequency of severe COVID-19 infection among ABO blood types.

RESULTS

A total of 227 cases were identified. Our cohort had a mean age of 63.3 years and 60% were males. The most common blood type was O (49%) followed by A (36%), which was similar to the prevalence of ABO blood types in our regional population. Moreover, there was no significant difference in the frequency of severe COVID-19 infection between ABO blood types (O: 50%, A: 53%, B: 56%, AB: 57%; P=0.93), or any additional outcomes including in-hospital mortality rate (P=0.72), need for ICU admission (P=0.66), ICU free days at day 28 (P=0.51), hospital free days at day 28 (P=0.43), or need for acute renal replacement therapy (P=0.09).

CONCLUSION

We did not find an increased susceptibility of any blood type to COVID-19 infection, nor was there an increased risk of severe COVID-19 infection in any ABO blood types.

ABO blood group and COVID-19: a review on behalf of the ISBT COVID-19 working group

Growing evidence suggests that ABO blood group may play a role in the immunopathogenesis of SARS-CoV-2 infection, with group O individuals less likely to test positive and group A conferring a higher susceptibility to infection and propensity to severe disease. The level of evidence supporting an association between ABO type and SARS-CoV-2/COVID-19 ranges from small observational studies, to genome-wide-association-analyses and country-level meta-regression analyses. ABO blood group antigens are oligosaccharides expressed on red cells and other tissues (notably endothelium). There are several hypotheses to explain the differences in SARS-CoV-2 infection by ABO type. For example, anti-A and/or anti-B antibodies (e.g. present in group O individuals) could bind to corresponding antigens on the viral envelope and contribute to viral neutralization, thereby preventing target cell infection. The SARS-CoV-2 virus and SARS-CoV spike (S) proteins may be bound by anti-A isoagglutinins (e.g. present in group O and group B individuals), which may block interactions between virus and angiotensin-converting-enzyme-2-receptor, thereby preventing entry into lung epithelial cells. ABO type-associated variations in angiotensin-converting enzyme-1 activity and levels of von Willebrand factor (VWF) and factor VIII could also influence adverse outcomes, notably in group A individuals who express high VWF levels. In conclusion, group O may be associated with a lower risk of SARS-CoV-2 infection and group A may be associated with a higher risk of SARS-CoV-2 infection along with severe disease. However, prospective and mechanistic studies are needed to verify several of the proposed associations. Based on the strength of available studies, there are insufficient data for guiding policy in this regard.

Low Levels of Natural Anti-α-N-Acetylgalactosamine (Tn) Antibodies Are Associated With COVID-19

Human serum contains large amounts of anti-carbohydrate antibodies, some of which may recognize epitopes on viral glycans. Here, we tested the hypothesis that such antibodies may confer protection against COVID-19 so that patients would be preferentially found among people with low amounts of specific anti-carbohydrate antibodies since individual repertoires vary considerably. After selecting glycan epitopes commonly represented in the human anti-carbohydrate antibody repertoire that may also be expressed on viral glycans, plasma levels of the corresponding antibodies were determined by ELISA in 88 SARS-CoV-2 infected individuals, including 13 asymptomatic, and in 82 non-infected controls. We observed that anti-Tn antibodies levels were significantly lower in patients as compared to non-infected individuals. This was not observed for any of the other tested carbohydrate epitopes, including anti-αGal antibodies used as a negative control since the epitope cannot be synthesized by humans. Owing to structural homologies with blood groups A and B antigens, we also observed that anti-Tn and anti-αGal antibodies levels were lower in blood group A and B, respectively. Analyses of correlations between anti-Tn and the other anti-carbohydrates tested revealed divergent patterns of correlations between patients and controls, suggesting qualitative differences in addition to the quantitative difference. Furthermore, anti-Tn levels correlated with anti-S protein levels in the patients' group, suggesting that anti-Tn might contribute to the development of the specific antiviral response. Overall, this first analysis allows to hypothesize that natural anti-Tn antibodies might be protective against COVID-19.

Association of the ABO blood group with SARS-CoV-2 infection in a community with low infection rate

Background and objectives

Reports on the association of the ABO phenotypes with infection by the SARS‐CoV‐2 virus have mostly come from countries with high infection rates. This study examined the possible association between SARS‐CoV‐2 infection and the ABO phenotype in Black Africa.

Materials and methods

This report is from a single centre where both asymptomatic and symptomatic patients were quarantined. At the time of this report, Oyo State, Nigeria had carried out 15 733 tests of which 3119 were positive for the virus with 1952 recoveries and 37 deaths. The ABO distribution of patients was compared with that of a blood donor population.

Results

Of the 302 participants, 297 (98%) had their blood group determined, asymptomatic and symptomatic individuals were 123 (40·7%) and 179 (59·3%) respectively. Blood group O was significantly less represented among the patients (P < 0·01) while blood groups B and AB were significantly more represented (P < 0·01, P = 0·03 respectively). Patients with anti‐B (groups A and O) were significantly less represented than those without anti‐B (B and/or AB): B and AB (P < 0·001), B (P = 0·002), AB (P = 0·01). There was no difference in the blood group distribution of symptomatic and asymptomatic patients (χ² (3, N = 302) = 2·29; P = 0·51), but symptomatic patients with anti‐A (groups B and O) were more represented than asymptomatic patients with anti‐A (χ² 4·89; P = 0·03).

Conclusion

The higher prevalence of blood group O and more potent beta haemolysins (anti‐B antibodies) are likely reasons for the lower infectivity by the SARS‐CoV‐2 virus and severity of COVID‐19 disease in the community.

ABO blood group and SARS-CoV-2 antibody response in a convalescent donor population

Background and Objectives

ABO blood group may affect risk of SARS‐CoV‐2 infection and/or severity of COVID‐19. We sought to determine whether IgG, IgA and neutralizing antibody (nAb) to SARS‐CoV‐2 vary by ABO blood group.

Materials and Methods

Among eligible convalescent plasma donors, ABO blood group was determined via agglutination of reagent A1 and B cells, IgA and IgG were quantified using the Euroimmun anti‐SARS‐CoV‐2 ELISA, and nAb titres were quantified using a microneutralization assay. Differences in titre distribution were examined by ABO blood group using non‐parametric Kruskal–Wallis tests. Adjusted prevalence ratios (aPR) of high nAb titre (≥1:160) were estimated by blood group using multivariable modified Poisson regression models that adjusted for age, sex, hospitalization status and time since SARS‐CoV‐2 diagnosis.

Results

Of the 202 potential donors, 65 (32%) were blood group A, 39 (19%) were group B, 13 (6%) were group AB, and 85 (42%) were group O. Distribution of nAb titres significantly differed by ABO blood group, whereas there were no significant differences in anti‐spike IgA or anti‐spike IgG titres by ABO blood group. There were significantly more individuals with high nAb titre (≥1:160) among those with blood group B, compared with group O (aPR = 1·9 [95%CI = 1·1–3·3], P = 0·029). Fewer individuals had a high nAb titre among those with blood group A, compared with group B (aPR = 0·6 [95%CI = 0·4‐1·0], P = 0·053).

Conclusion

Eligible CCP donors with blood group B may have relatively higher neutralizing antibody titres. Additional studies evaluating ABO blood groups and antibody titres that incorporate COVID‐19 severity are needed.

ABO Blood Types and COVID-19: Spurious, Anecdotal, or Truly Important Relationships? A Reasoned Review of Available Data

Since the emergence of COVID-19, many publications have reported associations with ABO blood types. Despite between-study discrepancies, an overall consensus has emerged whereby blood group O appears associated with a lower risk of COVID-19, while non-O blood types appear detrimental. Two major hypotheses may explain these findings: First, natural anti-A and anti-B antibodies could be partially protective against SARS-CoV-2 virions carrying blood group antigens originating from non-O individuals. Second, O individuals are less prone to thrombosis and vascular dysfunction than non-O individuals and therefore could be at a lesser risk in case of severe lung dysfunction. Here, we review the literature on the topic in light of these hypotheses. We find that between-study variation may be explained by differences in study settings and that both mechanisms are likely at play. Moreover, as frequencies of ABO phenotypes are highly variable between populations or geographical areas, the ABO coefficient of variation, rather than the frequency of each individual phenotype is expected to determine impact of the ABO system on virus transmission. Accordingly, the ABO coefficient of variation correlates with COVID-19 prevalence. Overall, despite modest apparent risk differences between ABO subtypes, the ABO blood group system might play a major role in the COVID-19 pandemic when considered at the population level.

The impact of ABO blood group on COVID-19 infection risk and mortality: A systematic review and meta-analysis

The 2019 coronavirus disease (COVID-19) has become a global pandemic. Several studies report that ABO blood group polymorphism may be related to COVID-19 susceptibility and clinical outcomes; however, the results are controversial. We conducted a systematic review and meta-analysis to investigate whether ABO blood groups are associated with increased COVID-19 morbidity and mortality. A total of 715 articles were retrieved from seven databases. Ten articles were selected for meta-analysis after removal of duplicates and two levels of screenings. Overall, individuals with blood group A [odds ratio (OR) = 1.33, 95% confidence interval (CI) 1.14 to 1.56] and B (OR = 1.06, 95% CI 1.00 to 1.13) had a substantially higher risk of COVID-19, whereas this was not the case for blood group AB (OR = 1.07, 95% CI 0.88 to 1.30). Individuals with blood group O was not prone to develop the disease (OR = 0.71, 95% CI 0.60 to 0.84). Moreover, the risk of COVID-19 was significantly associated with the Rh-positive blood group (OR = 1.22, 95% CI 0.99 to 1.50). A meta-analysis of 5 studies suggested that blood group A was associated with a significantly increased risk of COVID-19 mortality (OR = 1.25, 95% CI 1.02 to 1.52). Mild publication bias was found in the included studies. This systematic review and meta-analysis indicated that blood groups A and B may be risk factors for COVID-19, whereas the blood group O appears to be protective. Blood group A may be related to unfavourable outcomes. Further rigorous and high-quality research evidence is needed to confirm this association.

Relationship between the ABO blood group and COVID-19 susceptibility, severity and mortality in two cohorts of patients

BACKGROUND

Several articles reported the existence of an association between ABO blood groups and COVID-19 susceptibility. Group A and group O individuals showed a higher and lower risk, respectively, of becoming infected. No association was observed between ABO groups and mortality. To verify this association, we performed a retrospective study of two cohorts of patients with different demographic and clinical characteristics.

MATERIAL AND METHODS

A total of 854 regular blood donors were recruited for convalescent plasma donation after recovering from a mild COVID-19 infection, and a group of 965 patients more severely affected who were transfused during hospitalisation were also included. We also investigated the potential role of the different risk factors on patient outcome and death. To eliminate the confounding effect of risk factors on mortality, a propensity score analysis was performed.

RESULTS

Blood group A and blood group O COVID-19 blood donors showed a higher and lower risk, respectively, for acquiring COVID-19. In contrast, this association was not found in the group of patients transfused during hospitalisation, probably due to the great differences in demographic and clinical characteristics between the two groups. Regarding severity, age was one of the most significant risk factors. ABO blood groups were also seen to represent important risk factors for COVID-19 severity and mortality. Mortality risk in group A individuals was significantly higher than in group O individuals (OR: 1.75, 95% CI: 1.22-2.51).

DISCUSSION

The association between the ABO blood groups and the susceptibility to acquire COVID-19 infection was confirmed in the group of blood donors. ABO blood groups were also associated to COVID-19 severity and mortality in the group of patients transfused during hospitalisation. Therefore, blood groups A and O are two important factors to be considered when evaluating the prognosis of patients with COVID-19.

The association between ABO blood group and SARS-CoV-2 infection: A meta-analysis

At present, existing evidence about the association between SARS-CoV-2 infection and ABO blood group polymorphism is preliminary and controversial. In this meta-analysis we investigate this association and determine SARS-CoV-2 positive individuals' odds of having a specific blood group compared to controls. We performed a systematic search on MEDLINE and LitCovid databases for studies published through July 15, 2020. Seven studies met inclusion criteria for meta-analysis, including a total of 13 subgroups of populations (7503 SARS-CoV-2 positive cases and 2962160 controls). We analysed the odds of having each blood group among SARS-CoV-2 positive patients compared with controls. Random-effects models were used to obtain the overall pooled odds ratio (OR). Subgroup and sensitivity analyses were performed in order to explore the source of heterogeneity and results consistency. The results of our meta-analysis indicate that SARS-CoV-2 positive individuals are more likely to have blood group A (pooled OR 1.23, 95%CI: 1.09-1.40) and less likely to have blood group O (pooled OR = 0.77, 95%CI: 0.67-0.88). Further studies are needed to investigate the mechanisms at the basis of this association, which may affect the kinetics of the pandemic according to the blood group distribution within the population.