New Study shows blood type is factor in infection

The study also indicated that most blood type A patients were most likely to have the disease progress into severe or critical stages compared to the rest of the blood groups.( https://www.medrxiv.org/content/10.1101/2020.03.11.20031096v1.full.pdf+html)
 
The study which is not peer-reviewed, was led by Dr Jiao Zhao from the School Of Medicine at Shenzhen University of Science and Technology and involved a meta-analysis study of the tested records of 2 713 patients from three tertiary hospitals in Wuhan and Shenzhen.
 
The ABO group in 3694 normal people in Wuhan showed a distribution of 32.16%, 24.90%, 9.10% and 33.84% for A, B, AB and O, respectively, versus the distribution of 37.75%, 26.42%, 10.03% and 25.80% for A, B, AB and O, respectively, in 1,775 COVID-19 patients from Wuhan Jinyintan Hospital. The proportion of blood group A and O in COVID-19 patients were significantly higher and lower, respectively, than that in normal people (both P < 0.001).
 
Similar ABO distribution pattern was observed in 398 patients from another two hospitals in Wuhan and Shenzhen. Meta-analyses on the pooled data showed that blood group A had a significantly higher risk for COVID-19 (odds ratio-OR, 1.20; 95% confidence interval-CI 1.02~1.43, P = 0.02) compared with non-A blood groups, whereas blood group O had a significantly lower risk for the infectious disease (OR, 0.67; 95% CI 0.60~0.75, P < 0.001) compared with non-O blood groups. In addition, the influence of age and gender on the ABO blood group distribution in patients with COVID-19 from two Wuhan hospitals (1,888 patients) were analyzed and found that age and gender do not have much effect on the distribution.
 
The findings also showed that those with blood type O had the lowest risk of contracting the Covid-19 disease compared with non-O groups.
 
It was noted that during the SARS-CoV outbreak in 2003, a peer-reviewed study published in JAMA also showed that the SARS virus also exhibited a similar trait in which the group O individuals had a lower risk of contracting the disease. (https://www.ncbi.nlm.nih.gov/pubmed/15784866)
 
A study published in the Glycobiology journal in 2005  (https://www.ncbi.nlm.nih.gov/pubmed/18818423)  found that anti-A antibodies specifically inhibited the adhesion of SARS-CoV S protein-expressing cells to ACE2-expressing cell lines8 . Given the nucleic acid sequence similarity9 and receptor angiotensin-converting enzyme 2 (ACE2) binding similarity between SARS-CoV and SARS-CoV-210-12, the lower susceptibility of blood group O and higher susceptibility of blood group A for COVID-19 could be linked to the presence of natural anti-blood group antibodies, particularly anti-A antibody, in the blood. This hypothesis will need direct studies to prove. There may also be other mechanisms underlying the ABO blood group-differentiated susceptibility for COVID-19 that require further studies to elucidate.
 
The authors of the study state that this study may have potential clinical implications given the current COVID-19 crisis.
 
The first is that individuals with blood group A might need particularly strengthened personal protection to reduce the chance of infection.
 
The second is that SARS-CoV-2-infected patients with blood group A might need to receive more vigilant surveillance.
 
The third is that it might be helpful to introduce ABO blood typing in both patients and medical personal as a routine part of the management of SARS-CoV-2 and other coronavirus infections, to help define the management options and assess risk exposure levels of people.
 
The researchers cautioned however that it should be emphasized that due certain limitations, one should be cautious to use this study to guide clinical practice at this time. This study encourages further studies.

https://www.thailandmedical.news/news/breaking-coronavirus-research-reveals-that-people-with-blood-type-a-have-higher-risk-of-contracting-covid-19-compared-to-blood-type-o-which-has-a-low

Seems that blood type played a factor in the SARS outbreak as well as eluded to in the following abstract.

Severe acute respiratory syndrome (SARS) is caused by the SARS coronavirus (SARS-CoV), an RNA virus. The original SARS outbreak in the winter of 2002 to 2003 infected >8,000 individuals worldwide, with a fatality rate of 10% (292). Like other human coronaviruses, SARS-CoV infects the mucosal epithelium, causing an acute respiratory illness often accompanied by gastroenteritis. In a Hong Kong outbreak, there was an apparent association between disease transmission and ABO type (293). An epidemiology study of 34/45 hospital workers who contracted SARS after exposure to a single index patient showed that most of the infected individuals (23/34) were non-group O individuals (groups A, B, and AB). Group O individuals were relatively resistant to infection, with an OR of 0.18 (95% CI, 0.04 to 0.81; P = 0.03).

Like HIV, coronavirus is an enveloped virus that targets host cells via a viral adhesion glycoprotein. The SARS-CoV spike (S) protein is a 210- to 230-kDa glycoprotein with 23 potential N-glycosylation sites (292). Glycan analysis shows a wide range of structures, including complex N-glycans with 2 to 4 antennae capable of supporting ABH epitopes (292, 294). Because the virus targets respiratory and gastrointestinal mucosa, it is highly likely that most human isolates express ABH antigens on the S protein and host envelope GSLs. Like the Env protein, S protein expressing A antigen can be blocked by monoclonal anti-A and human anti-A (292).

Based on both epidemiologic and in vitro studies, Guillon et al. hypothesized that group O individuals are more resistant to SARS-CoV due to ABO antibodies and could decrease the rate of infection throughout the population (292). The degree of protection, however, may be influenced by the ABO antibody titer, secretor status, and incidence of group O in the population. Studies with human anti-A showed effective blocking with higher-titer anti-A (≥1:256) only; low-titer anti-A was ineffective (292). The latter finding has implications for individuals in industrialized countries, who tend to have low ABO titers (89). A nonsecretor phenotype would also nullify viral neutralization, since virus transmitted from a nonsecretor lacks ABH express

Common as dirt me O+  

Lovely. Here I sit, all A-.  

O-here

I think during the bubonic plague O blood type faired better than other types.....