A new nationwide study of the blood of more than 28,000 dialysis patients may help answer one of the big questions surrounding the pandemic: how many people have antibodies to SARS-CoV-2, the novel coronavirus? The answer could tell us a lot about how many people in the United States have been exposed to the virus and how much community spread there has been. … The short answer to how many people had antibodies, as of July, is approximately 9.3% -- although numbers ranged from an average of 3.5% in the West to an average of 27% in the Northeast.