According to recent data released by the American Red Cross, in the first week of March 2021 more than 20% of blood donations from unvaccinated people in the US had COVID-19 antibodies.
Between mid-June 2020 and early March 2021, the American Red Cross tested more than 3.3 million donations from unvaccinated people in 44 states to see whether COVID-19 antibodies were present. Overall, about 7.5% of the donations tested in that time frame were positive for COVID-19 antibodies, meaning that the donors had likely been infected with the coronavirus at a certain point.
The American Red Cross notes that a positive antibody test result does not confirm infection or immunity, but it may indicate whether a person has been exposed to the coronavirus, regardless of whether an individual developed symptoms. The antibody prevalence among unvaccinated blood donors increased over time, as cases grew across the country.
These data suggest that a considerable part of the US blood donor population has experienced COVID, knowingly or unknowingly. They also may or may not indicate that patients who are frequent blood recipients due to their condition, such as individuals with transfusion-dependent thalassaemia (TDT), could be at least partially protected against coronavirus by acquiring antibodies from the exposure to multiple blood donors, thus to have developed a so called ‘’passive immunity’’. Perhaps this explains partly, and in the absence of other reliable figures and data to date, the relatively low rates of infection and/or mild response to COVID-19 infection that has been observed in the majority of TDT patients.