Revisiting the Association of ABO Blood Groups Alongside Vaccination With Patient Outcomes in SARS‐CoV‐2 Respiratory Infection: A Prospective Observational Cohort Study in Bristol, UK 2020–2023

Background:

The 2023 SARS-CoV-2 environment differs greatly from the initial outbreak, with new variants and widespread vaccination. Early in the pandemic, blood group A was linked to increased hospitalisation and poor outcomes, but its role now, since the availability of vaccination, is unclear.

Methods:

We analysed data (1 August 2020–31 July 2023) from a prospective cohort of adults hospitalised in Bristol with SARS-CoV-2 and known ABO group (n = 3413). Admission date acted as a proxy for viral strain. Regression models assessed length of stay, survival, cardiovascular complications and ICU admission in non-O groups versus Group O.

Results:

Group A was over-represented and Group O was under-represented, compared to the blood donor population, except during Alpha dominance (p < 0.001; Alpha: p = 0.796). ABO group generally did not affect cardiovascular risk. However, during Wild-Type, Group AB had higher odds of cardiovascular complications (odds ratio [OR] = 3.18, p = 0.060) and intensive care unit [ICU] admission (OR = 4.79, p = 0.013). During Omicron, AB group patients had lower 30-day survival (HR = 2.09, p = 0.018). Group A was less likely to be discharged during Alpha (HR = 0.85, p = 0.013), while Group B was more likely to be discharged during Omicron (HR = 1.30, p = 0.002).

Conclusions:

ABO groups may still influence hospitalisation risk but appear less relevant to outcomes once admitted, likely reflecting advances in care and vaccination.