Less than 10% of a nationally representative sample of US dialysis patients had antibodies against COVID-19, showing that herd immunity will remain out of reach for quite some time, according to a study published late last week in The Lancet.Researchers from Stanford University and Ascend Clinical Laboratories tested the serum of 28,503 patients receiving treatment at 1,300 dialysis centers in 1,013 counties (32% of all US counties) in 46 states in July to estimate how many had been exposed to COVID-19.Substantial regional variationThey found that 8.2% to 9.4% of the sample had COVID-19 antibodies, indicating exposure to the virus.