Few in population developed COVID-19 antibodies in first wave, research suggests

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A cross-sectional, nationwide analysis of more than 28,000 patients on dialysis in the United States found that fewer than 10 percent of U.S. adults had novel coronavirus (COVID-19) antibodies as of July 2020 and fewer than 10 percent were diagnosed, according to new research published in The Lancet. The new study also showed higher COVID-19 infection rates among ethnic minorities and people living in lower-income, high density, urban areas, underling the need for COVID-19 public health efforts that prioritize these populations to prevent general community spread.

In the study, researchers tested the seroprevalence of SARS-CoV-2 antibodies in a randomly selected representative sample of 28,503 patients to provide a nationwide estimate of exposure to SARS-CoV-2 during the first wave of the pandemic. Of the sample population, 89 percent were tested in the first two weeks of July. The sampling was representative of U.S. patients on dialysis distributed by age, sex, race, ethnicity, and region, with the exception that these sampled patients were less likely to be non-Hispanic Blacks compared to the general U.S. adult population. Patients in the sample lived in 46 states and 1,013 U.S. counties.

Accounting for the externally validated test sensitivity, seroprevalence ranged from 8.2 percent to 9.4 percent in the sampled population. Researchers estimated the SARS-CoV-2 standardized seroprevalence in the U.S. population to be approximately 9.3 percent. The authors also found significant regional variation from less than 5 percent in the western United States to greater than 25 percent in the northeast.

By comparing seroprevalence data from their study with case counts per 100,000 population from Johns Hopkins University, the authors estimate that 9.2 percent of seropositive patients were diagnosed.

The authors note several limitations, including that the process of undergoing in-center hemodialysis might include the use of public or non-public shared transportation to and from the facility, thus increasing the potential for exposure. Conversely, because patients on dialysis are less likely to be employed and more likely to have restricted mobility, the data might underestimate overall seroprevalence in the general population. Finally, patients receiving dialysis may have more likely died or been hospitalized due to complications of SARS-CoV-2 infection. If so, these patients would not have been present for testing in the dialysis facilities, creating a survival bias and yielding lower estimates of exposure, the researchers said.

Despite these limitations, the researchers said the study shows that a surveillance strategy relying on monthly testing of the remainder plasma of patients receiving dialysis can produce useful estimates of SARS-CoV-2 spread inclusive of hard-to-reach, disadvantaged populations in the U.S. Such surveillance can inform disease trends, resource allocation, and effectiveness of community interventions during the COVID-19 pandemic.

"This research clearly confirms that despite high rates of COVID-19 in the United States, the number of people with antibodies is still low and we haven't come close to achieving herd immunity,” Julie Parsonnet, MD, study author and a professor of medicine at Stanford University. “Until an effective vaccine is approved, we need to make sure our more vulnerable populations are reached with prevention measures.”  

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