Fewer than 1 in 10 Americans showed signs of a prior coronavirus infection as of late July, suggesting that the "vast majority" of the population remains susceptible to the virus, according to a large national study published Friday in the Lancet.
The researchers arrived at their findings by studying the prevalence of coronavirus antibodies, which the immune system typically generates in response to an infection, in a group of randomly selected dialysis patients across the country. Even people with coronavirus antibodies are not necessarily immune to the virus, as scientists are still trying to understand how much protection antibodies create and how long that protection might last.
The finding that more than 90% of the country does not have antibodies is in line with conclusions of another study by the Centers for Disease Control and Prevention, which has not yet been published, according to CDC Director Dr. Robert Redfield.
Taken together, the two findings indicate that despite the high level of spread of the coronavirus throughout the spring and summer, much of the U.S. has yet to be infected. That means the country likely remains far off from herd immunity, which is reached when enough of the population has developed protection against the virus so that it cannot spread efficiently.
"If we're measuring herd immunity by antibodies, then this study does not support that there is herd immunity," said Shuchi Anand, a nephrologist at Stanford University who is the co-author of the new study.
Anand and co-author Maria Montez-Rath, a biostatistician at Stanford, said the study also indicated to what degree the virus has disproportionately infected Black and Hispanic people in the U.S. The CDC has previously acknowledged the disproportionate burden of infection in racial and ethnic minorities.
The new study found that people were more than twice as likely to have developed antibodies in Hispanic-majority communities than in mostly White communities and the rate was nearly four-fold in majority Black communities, Montez-Rath said.
The researchers were composed of a team from Stanford University and Ascend Clinical laboratory, which processes lab tests for kidney dialysis patients. They examined blood plasma samples from a randomly selected group of about 28,500 patients across 1,300 centers in 46 states.
The study found that about 8% of patients had developed coronavirus antibodies. Anand added that when adjusted for the general population, the study suggests about 9% of the public has antibodies. They noted that the prevalence of antibodies varied across regions of the country, with about 3.5% of patients in the West and more than 27% of patients in the Northeast showing signs of a prior infection.
"It tracks with what we know about the virus, that it was very intense in the northeast and it's sort of moving throughout the country now, but the the data is from July," Anand said, adding that more people have likely been exposed in the South and West, in particular, since then.
Eli Rosenberg, an epidemiologist at the State University of New York at Albany who was not part of the study, but has conducted similar antibody studies in New York, raised the question of whether the population of dialysis patients truly reflects that of the general population.
"It's a huge leap from dialysis to general adults," he said, adding that because of their underlying condition they may be more susceptible to infection and that these patients might have not been able to stay at home to avoid infection. "If you're going to a dialysis center rather than home dialysis, you don't have the luxury of sheltering in March or April."
Regardless, he said, the study is in line with other findings that the U.S. remains far from herd immunity.
"We'd have to experience a lot more illness and death to get to herd immunity and I think it should be morally unacceptable," he said. "If it took 200,000 deaths to get to something sort of like this, I mean, how many more deaths? We're talking a million or north of a million."
Most scientists say 60% to 80% of the population needs to be vaccinated or develop antibodies through natural infection to achieve herd immunity, top World Health Organization officials have previously said.
Critics of business closures and public health restrictions meant to curb the spread of the virus have pointed to herd immunity without a vaccine as a potential solution to the pandemic. However, WHO officials and many epidemiologists have criticized the strategy because it would likely lead to widespread disease and death.
The new study comes days after Redfield of the CDC told lawmakers that the majority of the country remains susceptible to the virus.
"The preliminary results in the first round show that a majority of our nation, more than 90% of the population, remains susceptible," he said Wednesday at a Senate hearing hosted by the Committee on Health, Education, Labor and Pensions. "A majority of Americans are still susceptible."
Dr. Scott Atlas, a neuroradiologist was brought on relatively recently by President Donald Trump to advise the White House's pandemic response, later challenged Redfield's remarks.
"It is not 90 percent of people that are susceptible to the infection," Atlas said Wednesday at a White House press briefing. He argued that people with antibodies represent "a small fraction of the people that have immunity," citing the theory that more people are protected against the coronavirus through T cells, a part of the immune system that defends against specific foreign pathogens.
Some scientists have said people might have T-cell protection due to exposure to other coronaviruses such as the common cold, but Director of the National Institute of Allergy and Infectious Diseases Dr. Anthony Fauci said such theories remain preliminary.
Fauci said on Friday that it was "extraordinarily inappropriate" for Atlas to "contradict" Redfield. He added that Atlas "tends to cherry pick data" and that the research on so-called cross immunity is not yet conclusive.
"You cannot assume that we are even anywhere near herd immunity right now in the United States," Fauci said. "We have a long way to go to get to herd immunity."