Less than 10% of Americans may have developed Covid-19 antibodies, study says vast majority still vulnerable
Fewer than 10% of Americans have developed antibodies against Covid-19 -- a sign of past infection -- by July 2020, suggesting a vast majority are still vulnerable to the disease, a new Lancet study suggests. Preliminary data from the Centers for Disease Control and Prevention (CDC) also have arrived at similar conclusions.
Similar data have emerged from other badly affected countries and regions such as Spain and China's Wuhan. Covid-19 has put an intense strain on resources, causing more deaths than usual during a typical year in the US. Despite that, fewer than 10% of US adults had formed antibodies to the virus in the first wave, researchers from Stanford University and Ascend Clinical Laboratory said.
"We are still in the middle of the fight,” Eli Rosenberg, a State University of New York at Albany epidemiologist who was not part of the study, told The Washington Post. “We’re all tired, and we’re all hoping for a vaccine. This shows us how it’s not over here, not even by a long shot.”
In this study, researchers studied antibody levels randomly from a selected group of 28,500 kidney dialysis patients from 46 states. They also included data on the participants' age, sex, race and ethnicity, and residence and facility ZIP codes from the anonymized electronic health records. They then extrapolated the results to the general US population.
The analysis showed that 9.3% of the American population might have antibodies against the disease. "It basically does show that a minority of the US population has evidence of antibodies to SARS-CoV-2 right now,” said study co-author Shuchi Anand, a nephrologist at Stanford University told Washington Post.
The study also found that antibody levels appeared to vary according to race. Antibody prevalence was high among predominantly Hispanic, non-Hispanic Black, and Hispanic and Black neighborhoods than the predominantly non-Hispanic white neighborhoods. "Public health efforts to limit SARS-CoV-2 spread need to especially target racial and ethnic minority and densely populated communities," they added.
The results are similar to a CDC study. “The preliminary results in the first round show that a majority of our nation, more than 90% of the population, remains susceptible,” Dr. Robert Redfield, said at a Senate hearing hosted by the Committee on Health, Education, Labor, and Pensions. “A majority of Americans are still susceptible."
The study indicates that the US is far from reaching herd immunity -- when a vast percentage of the population becomes immune to the disease either after developing the disease or getting a vaccine. Herd immunity could make it difficult for the virus to spread. However, study co-author Julie Parsonnet acknowledged that antibody studies are “not a perfect way” to track this, because a lot about immunity to Covid-19 is unclear. “We don’t really have perfect data that antibodies give immunity,” she said. “And we don’t have perfect data that there aren’t other forms of immunity that are also important,″ which antibody tests cannot detect.
The study has a few limitations. According to experts not involved in the study, extrapolating antibody levels in dialysis patients to the general population is problematic. They argue that the dialysis population's risk of exposure to SARS-CoV-2 is unlikely to be representative of the general population. "Attending a health-care facility three times a week would seem like a good way to encounter SARS-CoV-2, as has been shown elsewhere," Dr Barnaby Flower and Dr Christina Atchison from the Imperial College London, wrote in an accompanying editorial.
The study is published in The Lancet.