Official UK government report claims that 98% of adult blood donors have antibodies to COVID.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1031157/Vaccine-surveillance-report-week-44.pdf

“Based on antibody testing of blood donors, 98.0% of the adult population now have antibodies
to COVID-19 from either infection or vaccination compared to 18.7% that have antibodies from
infection alone.”