Less than 10 percent of Americans have antibodies to the new coronavirus, suggesting that the nation is even further from herd immunity than had been previously estimated, according to a study published Friday in The Lancet.

The study looked at blood samples from 28,500 patients on dialysis in 46 states, the first such nationwide analysis.

The results roughly matched those of an analysis to be released next week by the Centers for Disease Control and Prevention, which found that about 10 percent of blood samples from sites across the country contained antibodies to the virus.

Dr. Robert R. Redfield, the director of the C.D.C., was referring to that analysis when he told a congressional committee this week that 90 percent of all Americans were still vulnerable to the virus, a C.D.C. spokeswoman said.

An accurate estimate of the country’s immunity is important because President Trump, in collaboration with his new medical adviser, Dr. Scott Atlas, has tentatively promoted the idea of reaching herd immunity by canceling lockdowns, mask-wearing campaigns and social-distancing mandates. The plan would be to let the virus wash through the population while attempting to protect the people deemed most vulnerable.

Most public health experts say that such a policy would lead to hundreds of thousands more deaths, as it is impossible to protect all Americans who are elderly or have one of a dozen underlying conditions, including diabetes and heart disease, that render a person more likely to become seriously ill or to die.

The study of dialysis patients was done by scientists from Stanford University and published in The Lancet.

It found wide variances in antibody levels around the country. In the New York metropolitan area, including New Jersey, antibody levels were higher than 25 percent of samples tested. In the western United States, they were below 5 percent.

Over all, the researchers estimated the prevalence to be about 9.3 percent.

Dialysis patients are not necessarily representative of the whole population, and the study is just one of many attempts to land on an accurate estimate of seroprevalence.

The C.D.C. study, which has not yet been released, was described by a C.D.C. spokeswoman. It involved testing blood samples collected at 52 commercial laboratories between early July and mid-August in all 50 states, the District of Columbia and Puerto Rico.

Based on 46 sites with the most data, C.D.C. researchers concluded that the overall national prevalence rate was less than 10 percent. The prevalence rate ranged from lows of less than 1 percent in some states to about 22.5 percent in New York State.

The implication of the antibody studies, Dr. Redfield said in a statement, is that the vast majority of Americans are still susceptible to the virus and therefore should continue to take steps such as wearing masks, staying six feet away from other people, washing hands frequently, staying home when sick and “being smart about crowds.”

NYTIMES

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