ABO blood group as a determinant of COVID-19 and Long COVID: An observational, longitudinal, large study.

BACKGROUND: An association of ABO blood group and COVID-19 remains controversial. METHODS: Following STROBE guidance for observational research, we explored the distribution of ABO blood group in patients hospitalized for acute COVID-19 and in those with Long COVID. Contingency tables were made and risk factors were explored using crude and adjusted Mantle-Haentzel odds ratios (OR and 95% CI). RESULTS: Up to September 2022, there were a total of 5,832 acute COVID-19 hospitalizations in our hospital, corresponding to 5,503 individual patients, of whom blood group determination was available for 1,513 (27.5%). Their distribution by ABO was: 653 (43.2%) group 0, 690 (45.6%) A, 113 (7.5%) B, and 57 (3.8%) AB, which corresponds to the expected frequencies in the general population. In parallel, of 676 patients with Long COVID, blood group determination was available for 135 (20.0%). Their distribution was: 60 (44.4%) from group 0, 61 (45.2%) A, 9 (6.7%) B, and 5 (3.7%) AB. The distribution of the ABO system of Long COVID patients did not show significant differences with respect to that of the total group (p ≥ 0.843). In a multivariate analysis adjusting for age, sex, ethnicity, and severity of acute COVID-19 infection, subgroups A, AB, and B were not significantly associated with developing Long COVID with an OR of 1.015 [0.669-1.541], 1.327 [0.490-3.594] and 0.965 [0.453-2.058], respectively. The effect of the Rh+ factor was also not significant 1,423 [0.772-2,622] regarding Long COVID. CONCLUSIONS: No association of any ABO blood subgroup with COVID-19 or developing Long COVID was identified.

Association Between ABO Blood Group System and COVID-19 Severity.

OBJECTIVES: A possible association between blood group systems (ABO and Rh) and coronavirus disease 2019 (COVID-19) severity has recently been investigated by various studies with conflicting results. However, due to variations in the prevalence of the ABO and Rh blood groups in different populations, their association with COVID-19 might be varied as well. Therefore, we conducted this study on Libyan participants to further investigate this association and make population-based data available to the worldwide scientific community. METHODS: In this case-control study, ABO and Rh blood groups in 419 confirmed COVID-19 cases in Zawia, Libya, and 271 healthy controls were compared using descriptive statistics and χ 2 tests. RESULTS: Blood group A was significantly more prevalent in patients with severe COVID-19 (64/125; 51.2%) than in patients with nonsevere COVID-19 (108/294, 36.7%) (P < .034), whereas the O blood group prevalence was higher in nonsevere COVID-19 cases (131/294, 44.5%) compared with severe cases (43/125, 34.4%) (P < .001). CONCLUSIONS: The results showed a significant association between blood group A and the severity of COVID-19, whereas patients with blood group O showed a low risk of developing severe COVID-19 infection. No significant association was found between Rh and susceptibility/severity of the disease.

A Novel Targeted RIG-I Receptor 5'Triphosphate Double Strain RNA-Based Adjuvant Significantly Improves the Immunogenicity of the SARS-CoV-2 Delta-Omicron Chimeric RBD-Dimer Recombinant Protein Vaccine.

The rapid mutation and spread of SARS-CoV-2 variants recently, especially through the emerging variants Omicron BA5, BF7, XBB and BQ1, necessitate the development of universal vaccines to provide broad spectrum protection against variants. For the SARS-CoV-2 universal recombinant protein vaccines, an effective approach is necessary to design broad-spectrum antigens and combine them with novel adjuvants that can induce high immunogenicity. In this study, we designed a novel targeted retinoic acid-inducible gene-I (RIG-I) receptor 5'triphosphate double strain RNA (5'PPP dsRNA)-based vaccine adjuvant (named AT149) and combined it with the SARS-CoV-2 Delta and Omicron chimeric RBD-dimer recombinant protein (D-O RBD) to immunize mice. The results showed that AT149 activated the P65 NF-κB signaling pathway, which subsequently activated the interferon signal pathway by targeting the RIG-I receptor. The D-O RBD + AT149 and D-O RBD + aluminum hydroxide adjuvant (Al) + AT149 groups showed elevated levels of neutralizing antibodies against the authentic Delta variant, and Omicron subvariants, BA1, BA5, and BF7, pseudovirus BQ1.1, and XBB compared with D-O RBD + Al and D-O RBD + Al + CpG7909/Poly (I:C) groups at 14 d after the second immunization, respectively. In addition, D-O RBD + AT149 and D-O RBD + Al + AT149 groups presented higher levels of the T-cell-secreted IFN-γ immune response. Overall, we designed a novel targeted RIG-I receptor 5'PPP dsRNA-based vaccine adjuvant to significantly improve the immunogenicity and broad spectrum of the SARS-CoV-2 recombinant protein vaccine.

The role of blood groups, vaccine type and gender in predicting the severity of side effects among university students receiving COVID-19 vaccines.

On March 11th, 2020, the World Health Organization (WHO) declared the coronavirus disease 2019 (COVID-19) a pandemic. To control the pandemic, billions of vaccine doses have been administered worldwide. Predictors of COVID-19 vaccine-related side effects are inconsistently described in the literature. This study aimed to identify the predictors of side effects' severity after COVID-19 vaccination among young adult students at Taif University (TU) in Saudi Arabia. An online, anonymous questionnaire was used. Descriptive statistics were calculated for numerical and categorical variables. Possible correlations with other characteristics were identified using the chi-square test. The study included 760 young adult participants from TU. Pain at the injection site (54.7%), headache (45.0%), lethargy and fatigue (43.3%), and fever (37.5%) were the most frequently reported COVID-19 vaccine-related side effects after the first dose. The most frequent side effects were reported among the 20-25-year-old age group for all doses of all vaccines. Females experienced remarkably more side effects after the second (p < 0.001) and third doses (p = 0.002). Moreover, ABO blood groups significantly correlated with vaccine-related side effects after the second dose (p = 0.020). The participants' general health status correlated with the side effects after the first and second doses (p < 0.001 and 0.022, respectively). The predictors of COVID-19 vaccine-related side effects in young, vaccinated people were blood group B, female gender, vaccine type, and poor health status.

Association of ABO and RhD blood groups with the risk of HIV infection.

Naturally occurring antibodies against ABO antigens present in human sera have been shown to neutralize ABO-expressing HIV in vitro. We investigated associations between ABO and RhD blood groups and HIV infection among blood donors from all blood collection centers in eight of South Africa's nine provinces. Whole blood donations collected from first time donors between January 2012 and September 2016 were tested for HIV RNA by nucleic acid testing and HIV antibody using third generation serology assays. ABO and RhD blood types were determined using automated technology. Odds ratios for the association between HIV positivity and ABO and RhD phenotypes were calculated using multivariable logistic regression analysis. We analyzed 515,945 first time blood donors and the overall HIV prevalence was 1.12% (n = 5790). After multivariable adjustment, HIV infection was weakly associated with RhD positive phenotype (OR = 1.15, 95% CI 1.00-1.33) but not with ABO blood group. The observed association with RhD positive phenotype was marginal and likely due to residual confounding by racial group but could serve to generate hypotheses for further studies.

Relationship between the ABO blood group and Rhesus factors with COVID-19 susceptibility.

INTRODUCTION: The molecular research has raised copious hypotheses about different molecular effects on the variable expression of the current virus on the human body. The present prospective study aims to determine clinically as well as statistically, the relation between ABO blood groups and Rhesus (Rh) factor and the severity of the Covid-19 virus. RESEARCH DESIGN AND METHODS: We conducted a prospective, single-centered study at The Combined Military Hospital Lahore, Pakistan. Details of only those patients who exhibit COVID-19 symptoms were included. The odds ratios with a 95% confidence interval and the chi-square test of blood groups and Rhesus factor was also conducted individually with the severity of disease, outcomes, and respiratory symptoms. P-values less than 0.05 was considered significant. RESULTS: The chi-square test and odd ratio yielded no significant results when the covid-19 status was compared with the Rhesus factor (p-value > 0.05). However, the results were found to be significant when associations were run between Covid-19 status and all the blood groups (p-value < 0.05). CONCLUSION: According to the analytical results of the present study, protective nature of all the blood antigens (A, B, AB, none) was observed in patients presenting with Covid-19 symptoms of varying severity.

The association of ABO blood group distribution and clinical characteristics in patients with SARS-CoV-2.

INTRODUCTION: SARS-COV-2, the novel severe acute respiratory syndrome coronavirus, has become a life-threatening public health crisis. This kind of pandemic is frightening the world with clinical, psychological, and emotional distress and leading to an economic slowdown. To explore any association between the ABO blood type and the susceptibility to coronavirus disease 2019 (COVID-19), we compared ABO blood group distribution among 671 COVID-19 patients with the local control population. METHODOLOGY: The study was conducted in Blood Bank Hospital in Erbil, Kurdistan Region, Iraq. The ABO-typed blood samples were obtained from 671 patients infected with SARS-CoV-2 between February and June 2021. RESULTS: Our results demonstrated that the risk of SARS-COV-2 was higher for patients with blood group A than those with not-A blood type patients. Of the 671 patients with COVID-19, 301 had type A (44.86%), 232 had type B (34.58%), 53 had type AB blood (7.9%), and 85 had type O (12.67%). CONCLUSIONS: We concluded that the Rh-negative blood type has a protective effect on SARS-COV-2. Our results also indicate that the decreased susceptibility of individuals with blood group O and the increased susceptibility of individuals with blood group A to COVID-19 could be linked to the presence of natural anti-blood group antibodies, particularly anti-A antibody, in the blood. However, there might be other mechanisms that require further study.

Associations of ABO and Rhesus D blood groups with phenome-wide disease incidence: A 41-year retrospective cohort study of 482,914 patients.

Background: Whether natural selection may have attributed to the observed blood group frequency differences between populations remains debatable. The ABO system has been associated with several diseases and recently also with susceptibility to COVID-19 infection. Associative studies of the RhD system and diseases are sparser. A large disease-wide risk analysis may further elucidate the relationship between the ABO/RhD blood groups and disease incidence. Methods: We performed a systematic log-linear quasi-Poisson regression analysis of the ABO/RhD blood groups across 1,312 phecode diagnoses. Unlike prior studies, we determined the incidence rate ratio for each individual ABO blood group relative to all other ABO blood groups as opposed to using blood group O as the reference. Moreover, we used up to 41 years of nationwide Danish follow-up data, and a disease categorization scheme specifically developed for diagnosis-wide analysis. Further, we determined associations between the ABO/RhD blood groups and the age at the first diagnosis. Estimates were adjusted for multiple testing. Results: The retrospective cohort included 482,914 Danish patients (60.4% females). The incidence rate ratios (IRRs) of 101 phecodes were found statistically significant between the ABO blood groups, while the IRRs of 28 phecodes were found statistically significant for the RhD blood group. The associations included cancers and musculoskeletal-, genitourinary-, endocrinal-, infectious-, cardiovascular-, and gastrointestinal diseases. Conclusions: We found associations of disease-wide susceptibility differences between the blood groups of the ABO and RhD systems, including cancer of the tongue, monocytic leukemia, cervical cancer, osteoarthrosis, asthma, and HIV- and hepatitis B infection. We found marginal evidence of associations between the blood groups and the age at first diagnosis. Funding: Novo Nordisk Foundation and the Innovation Fund Denmark.

Optimal dose of rituximab in ABO-incompatible kidney transplantation in patients with low anti-A/B antibody titers: A single-center retrospective cohort study.

BACKGROUND: The clinical outcomes of ABO-incompatible (ABOi) kidney transplantation have improved with the introduction of desensitization therapy with rituximab. However, rituximab prevents not only antibody-mediated rejection (AMR) but also increases the risk of adverse events, such as infection. For ABOi kidney transplantation in patients with low anti-A/B antibody titers, we previously used a rituximab-free desensitization protocol and then initiated a single dose of 100 mg rituximab in 2016. We retrospectively compared the outcomes of ABOi kidney transplantation in patients with low anti-A/B antibody titers before and after the introduction of rituximab. METHODS: ABOi kidney transplantations (n = 142) in patients with low anti-A/B antibody titers between 2007 and 2021 were included. Patients were divided into two groups (with and without rituximab) for desensitization. The primary outcomes were the incidence of acute AMR and infection. RESULTS: Sixty-six patients were desensitized without rituximab (rituximab-free group), and 76 were pretreated with 100 mg rituximab (rituximab group) before transplantation. The incidence of acute AMR was significantly lower in the rituximab group than in the rituximab-free group (.0% [0/76] vs. 7.6% [5/66], respectively; p = .047). Post-transplantation anti-A/B antibody titers were also lower in the rituximab group than in the rituximab-free group. There was no significant difference in the incidence of adverse events, including infections, between the two groups. CONCLUSION: In ABOi kidney transplantation patients with low anti-A/B antibody titers, the desensitization protocol with a single dose of 100 mg rituximab was effective in preventing acute AMR without increasing the risk of other adverse events.

ABO-Incompatible Living Donor Liver Transplant From a Blood Type A2 Donor to a Type B Recipient: A Note of Caution.

Standardization of immunomodulation protocols has enabled ABO-incompatible liver transplants with outcomes similar to those of ABO-compatible liver transplants. Patients with the A2 blood group are unique because they have a diminished expression of the A antigen. Despite rare immune complications, this phenomenon of diminished expression has led to treatment of type A2 donors according to the regimen for type O blood group donors in ABO-incompatible liver transplants. Additionally, the requirement for pretransplant recipient immunomodulation is consi dered minimal when considering these donors. The transplant of a type A2 donor kidney to a type B recipient is well recognized; however, for liver donation the A2-to-B transplant is rare. Here, we present a case of 48-year-old male patient with blood group type B who underwent ABO-incompatible liver transplant of a right lobe liver graft from a type A2 donor. Postoperatively, despite adequate immunosuppression and initiation of thera - peutic plasma exchange, the patient developed severe and refractory antibody-mediated rejection that ultimately abated with a splenectomy. This report highlights the low but tangible risk of antibody-mediated rejection in ABO-incompatible liver transp lants from type A2 donors and emphasizes the importance of serial monitoring of anti-A isohemag glutinin titers and posttransplant splenectomy to ensure that liver grafts with antibody-mediated rejection can be rescued.

Association of blood group with COVID-19 disease susceptibility and severity in Saudi Arabia.

BACKGROUND: Novel SARS-CoV-2 (COVID-19) virus has rapidly spread worldwide and was declared a pandemic, making identifying and prioritizing individuals most at risk a critical challenge. The literature describes an association between blood groups and the susceptibility to various viral infections and their severity. Knowing if a specific blood group has more susceptibility to COVID-19 may help improve understanding the pathogenesis and severity of the disease. We aimed to assess the association between ABO/RhD and COVID-19 susceptibility and severity, and to compare results with similar studies in Saudi Arabia. STUDY DESIGN AND METHODS: This study was conducted between March and October 2021 on 600 patients confirmed positive for COVID-19 infection. Patients' data were collected and analyzed. As a control, 8423 healthy blood donors were enrolled as a sample representative of the population for blood group distribution. RESULTS: More individuals had blood group B in the COVID-19 group in comparison with the control group (24.2% vs. 18%), The opposite was observed among individuals of group O (39.5% vs. 47.3%). The B blood group was predictive of higher risk of mortality. No significant difference in the distribution of RhD was observed between the COVID-19 and the control groups. Neither ABO nor RhD was significantly associated with the severity of COVID-19. DISCUSSION: Although there was no significant association with the disease severity, the B blood group may be associated with a higher risk for COVID-19 infection. Further studies with a larger sample size are necessary to evaluate this correlation.

Use of ABO blood groups and co-morbidities as predictors of mortality in COVID-19 patients.

OBJECTIVE: This study aimed to investigate the mortality relationship between COVID-19 and ABO blood groups and comorbid diseases. The aim of this study was to determine whether ABO blood groups and comorbid diseases can be used as a prognostic factor for hospitalization. PATIENTS AND METHODS: This retrospective study included patients aged ≥ 18 years presenting to the adult emergency COVID-19 outpatient clinic. COVID-19 patients were divided into four stages according to their clinical status: mild, moderate, severe, and critical. Those with the comorbid disease were classified as Group I, and those without comorbid disease were classified as Group II. RESULTS: Of the 384 patients included in the study, 190 (49.5%) were male and 194 (50.5%) were female, with a mean age of 47.3 ± 18.4 years. The clinical data of the patients were scanned from the hospital automation system. Although the risk of transmission was higher, especially in people with A blood type, this rate was lower in the O blood group. The clinical course of the disease was more severe and the mortality rates were higher in the AB blood group (p < 0.001). In the hospital, 35 people who were treated for COVID-19 disease died. CONCLUSIONS: Certain ABO blood types and comorbid diseases were important risk factors for COVID-19 and were associated with mortality. We found that some ABO blood groups and comorbid diseases are associated with COVID-19 and may be important risk factors. While the risk of transmission of COVID-19 is high in blood group A, we think that the clinical course of COVID-19 may be more severe and the death rate higher in blood group AB.

EVALUATION OF HUMAN ABO BLOOD GROUPS AND BLOOD COMPONENTS AMONG IRAQI PATIENTS INFECTED WITH CORONAVIRUS DISEASE 2019 (COVID-19).

OBJECTIVE: The aim: To evaluate the differences in blood groups, gender and type of Rh factor, as well as the levels of hemoglobin, white blood cells and platelets among patients infected with COVID-19. PATIENTS AND METHODS: Materials and methods: A cross-sectional study was performed on 202 patients diagnosed with sever COVID-19 infection who were admitted to the Al-Shefaa center in Al- Hakeem hospital in Al-Najef city.Haematological investigations involved the types of blood groups, Rh factors, haemoglobin (Hb), white blood cells (WBCs), and platelets. In addition, the demographic features including age, gender and presence of any prescribed medications before or at the time of the study were also included. RESULTS: Results: This study indicated that COVID-19 infected patients with type A blood group are at higher risk of hospitalization than other blood groups, and the majority of these patients were Rh positive. Additionally, WBCs counts indicated that the majority of patients had increased risk of getting infections which demonstrated lower WBC counts than normal. Platelet and Hb levels were normal for the majority of patients. CONCLUSION: Conclusions: The findings of this study may help in the diagnosis of the pandemic infection with COVID-19, and prediction of the incidence of some complications caused by COVID-19. Further researches are warranted to confirm our findings.

The association between different blood group systems and susceptibility to COVID-19: a single center cross-sectional study from Saudi Arabia.

Background: Since the beginning of COVID-19 pandemic, many associated factors have been investigated to clarify the susceptibility and severity among the affected individuals. Biological markers can play an important role in identification of individual susceptibility to such pandemic. Growing evidence suggest the influence of different blood group systems on susceptibility to COVID-19 virus, with a particular blood type conferring selection advantage. Objectives: The study aimed to determine the association of ABO, Rhesus (D) and P1 blood groups with COVID-19 susceptibility in Taif city, Western Saudi Arabia. Methods: ABO, D and P1 blood antigens were determined in 104 blood samples of COVID-19 patients versus 100 control samples using either automated immunohematology analyser or test tube method. Statistical differences between patients and control samples were calculated based on p-value where results of ≤ 0.05 were considered significant. Results: O+ve blood group constituted the predominant type among the studied samples. Determination of P1 antigen showed significant association where Anti-P1 was positive in 76.9% of patients compared to 61.0% of controls with a P value of 0.01 conferring the susceptibility of P1+ve patients to COVID-19. Conclusion: Although our study showed no significant association between ABO and D, and susceptibility to COVID-19, there was a significant association between P1+ve and COVID-19. P1+ve participants were 2.131 times more associated with the risk of COVID-19 infection than those with Anti P1-ve. Thus, P1 antigen can be used as a biological marker for identification of individuals susceptibility to COVID-19. It is strongly advised that such individuals should consider extra protective measures. Further studies on other contributing factors should also be considered for more scientific clarity.

ABO rs657152 and Blood Groups Are as Predictor Factors of COVID-19 Mortality in the Iranian Population.

Several studies have discovered a relationship between specific blood types, genetic variations of the ABO gene, and coronavirus disease 2019 (COVID-19). Therefore, the aim of this study was to evaluate the association between ABO rs657152 polymorphisms and ABO blood groups with COVID-19 mortality. The tetraprimer amplification refractory mutation system, polymerase chain reaction method, was used for ABO rs657152 polymorphism genotyping in 1,211 dead and 1,442 improved patients. In the current study, the frequency of ABO rs657152 AA than CC genotypes was significantly higher in dead patients than in improved patients. Our findings indicated that blood type A was associated with the highest risk of COVID-19 mortality compared to other blood groups, and patients with blood type O have a lower risk of infection, suggesting that blood type O may be a protective factor against COVID-19 mortality. Multivariate logistic regression test indicated that higher COVID-19 mortality rates were linked with alkaline phosphatase, alanine aminotransferase, high density lipoprotein, low-density lipoprotein, fasting blood glucose, uric acid, creatinine, erythrocyte sedimentation rate, C-reactive protein, 25-hydroxyvitamin D, real-time PCR Ct values, ABO blood groups, and ABO rs657152 AA genotype. In conclusion, the AA genotype of ABO rs657152 and blood type A were associated with a considerably increased frequency of COVID-19 mortality. Further research is necessary to validate the obtained results.

Association between ABO blood groups and the risk of infection with SARS-CoV-2 in Iraq.

OBJECTIVE: The primary goals of this research were to analyze the relationship between ABO blood types and the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and investigate the effect of vaccination in Iraq. METHODS: Data and outcomes were gathered from the medical records of 200 patients. Patients were categorized by blood group and vaccination status in the analysis. RESULTS: In total, 200 hospitalized patients (125 men and 75 women) with confirmed SARS-CoV-2 infection and blood group (ABO) and clinical data were enrolled. Of the 200 patients, 155 (77.5%) were vaccinated against SARS-CoV-2. The results illustrated that 25 patients died, which might have been attributable to a lack of vaccination or older age. Our analysis revealed that blood group O individuals were much less likely to be infected by SARS-CoV-2 than non-O subjects, whereas blood group A individuals carried a higher risk of infection. CONCLUSIONS: Our findings illustrated that immunization significantly reduces COVID-19 risk across all age groups, but there has been an increase in the number of cases because of decreased vaccine efficacy in older patients and persons with comorbidities. However, 45% vaccination coverage lowered the outbreak's peak.

ABO-Rh Blood Types and Clinical Consequences of COVID-19 Infection.

Aim and Background: Because of there is no sufficient evidence showing a relationship between blood types and severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, this study was planned to investigate the effects of ABO blood group on the clinical outcomes of SARS-CoV-2 infection. Patients and Methods: The data of the patients were examined retrospectively. The patients who were hospitalized in wards or intensive care unit, constituted the study group. The patients who presented to the hospital because of other causes and whose blood type examinations were performed, were included in the control group. Results: The study group consisted of 406 six patients were diagnosed with SARS-CoV-2 infection. Control group consisted of 38079 patients whose blood group was determined for any reason in the same period. The rate of Rh negativity was significantly higher in the patient group (p = 0,01). Hospitalization duration in intensive care was significantly longer in the blood type A and AB groups compared to the blood type O group (p = 0,03). Conclusion: Our results are in agreement with other studies suggesting that blood group O individuals are somewhat more resistant to clinically overt infection with SARS-CoV-2 than other blood groups. In addition, Rh negativity may also be an individual risk factor for SARS-CoV-2 infection.

Blood phenotype O and indirect bilirubin are associated with lower, early COVID-19-related mortality: A retrospective study.

OBJECTIVES: To evaluate the ABO blood type and indirect bilirubin to predict early mortality in adults with severe COVID-19. METHODS: This retrospective observational study was conducted on 268 adult patients with laboratory-confirmed COVID-19 who had attended the intensive care unit (ICU), Quena general hospital and Luxor International Hospital, and other hospitals or centers for the treatment of COVID-19, during the period from January 2021 till December 2021. RESULTS: Relation between mortality and ABO group were highly significant, as we found non-O blood group with more risk of early mortality and intensive care unit admission ICU. There were significant differences between dead and alive cases as regards platelets, white blood cells WBCs (neutrophil, lymphocyte), albumin, liver enzymes aspartate transeferase (AST), alanine transferase (ALT), total direct and indirect bilirubin, creatinine, and urea. CONCLUSION: There was a highly significant relation between dead cases and ABO blood group as between the O and non-O groups; also, group O was associated with less severe manifestations and or ventilation and less mortality in patients with severe COVID-19 infection. Direct bilirubin >0.5 was found to be the best predictor for mortality in cases with COVID-19 so indirect bilirubin may be considered a good protector against complications of the infection.

COVID-19 infection and complications according to ABO blood group in the elderly: A population-based subcohort and meta-analysis.

BACKGROUND AND OBJECTIVES: It is reported that ABO antibodies have a role in COVID-19 infection and severity; however, ABO antibody titres vary with advanced age. The aim was to analyse the association between ABO blood group and risk of COVID-19 infection and complications in elderly patients, and to contrast this data with findings in the overall adult population. MATERIALS AND METHODS: A prospective cohort study of the Navarre (Spain) population aged ≥60 years and a meta-analysis of published studies including participants of ≥60 years were carried out. RESULTS: In the Navarre elderly population, a higher risk of COVID-19 infection was identified in the A versus non-A and O group and lower risk in O versus non-O, with no significant association between hospitalization, intensive care unit admission or mortality and any of the blood groups, results that coincide with those of the overall Navarre adult population. The meta-analyses using studies that included participants of ≥60 years demonstrated a higher risk of hospitalization and mortality in A versus non-A and a lower mortality risk with B versus non-B. Similar mortality results were found in the meta-analyses of the overall adult population. CONCLUSION: There are no relevant differences between the overall adult population and population aged ≥60 years in the risk of COVID-19 infection and severity according to ABO blood groups, suggesting that age-related changes in ABO would be of limited clinical significance.

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.