Several independent datasets suggest blood type A is over-represented and type O under24 represented among COVID-19 patients. Here, I model a scenario in which ABO transfusion incompatibility reduces the chance of a patient transmitting the virus to an incompatible recipient. Comparison of model outputs to published data on COVID-19 prevalence indicates that if this scenario holds true, ABO incompatibility may reduce virus transmissibility by 60% or more. Paradoxically, however, targeted vaccination of either high-susceptibility type A or “super spreader” type O individuals is less effective than random vaccination at blocking community spread of the virus. Instead, the key is to maintain blood type diversity amongst the remaining susceptible individuals. I stress that these results illustrate a theoretical model of ABO … Continue reading ABO incompatibility may reduce virus transmissibility by 60% or more