Few dialysis patients in the United States contracted infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus that causes COVID-19, during the first wave of the virus as reflected by the low percentage of the dialysis population testing positive for antibodies to the virus, according to findings from a new nationwide study.
In July 2020, investigators tested remaining plasma from 28,503 randomly selected patients receiving dialysis in the United States. They employed the Siemens spike protein receptor binding domain total antibody chemiluminescence assay, which has 100% sensitivity and 99.8% specificity for SARS-CoV-2 antibodies. The cohort was similar to the overall US dialysis population distributed by age, sex, race, ethnicity, and region.
SARS-CoV-2 seroprevalence was 8.0% in the cohort, 8.3% when standardized to the total US dialysis population, and 9.3% when standardized to the broader US adult population, Shuchi Anand, MD, MS, and colleagues from Stanford University in Palo Alto, California, reported in The Lancet. Of those testing positive, 76% were aged 45 to 79 years. In the US adult population, 79% of those estimated to be seropositive were aged 64 years or younger.
Only 9.2% of seropositive dialysis patients received a formal diagnosis of COVID-19 infection based on antigen or PCR testing, according to data-based estimates, Dr Anand’s team reported.
The investigators’ goal was to provide a nationwide estimate of exposure to SARS-CoV-2 during the first wave of COVID-19 in the United States up to July 2020. Sampled dialysis patients resided in 46 states and 1013 counties. Like all dialysis patients, they underwent routine blood testing without selection bias.
“Patients receiving dialysis might be considered an ideal sentinel population in which to study the evolution of the COVID-19 public health crisis,” Dr Anand’s team wrote.
They also observed, “Risk factors for acquisition of SARS-CoV-2 and for severe COVID-19, including advanced age, non-white race, poverty, and diabetes, are the rule rather than the exception in the US dialysis population.”
After standardization, seroprevalence in the US dialysis population ranged from 3.5% in the western region to 27.2% in the Northeast (with the highest seroprevalence in New York State at 33.6%). Residents of Black and Hispanic neighborhoods had 3.9- and 2.3-fold higher odds of seropositivity, respectively, compared with residents of largely White neighborhoods. Residents of neighborhoods with the highest quintile of population density (more than 8607 people per square mile) had 10.3-fold higher odds of seropositivity than residents of neighborhoods with the lowest quintile of population density (less than 349 people per square mile). By zip code area, a 30% or higher poverty level (vs 10% or lower poverty) was associated with 2.4-fold higher odds of seropositivity. In addition, counties that reduced workplace visits by 5% or more (vs less than 5%) in early March 2020 had 60% lower odds of seropositivity in July 2020.
“We were able to determine – with a high level of precision – differences in seroprevalence among patient groups within and across regions of the United States, providing a very rich picture of the first wave of the COVID-19 outbreak that can hopefully help inform strategies to curb the epidemic moving forward by targeting vulnerable populations,” Dr Anand stated in a press release from The Lancet.
Study co-author Julie Parsonnet, MD, highlighted the ongoing threat.
“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,” Dr Parsonnet stated. “Until an effective vaccine is approved, we need to make sure our more vulnerable populations are reached with prevention measures.”
COVID-19 control efforts should prioritize ethnic minorities and people living in densely populated areas to prevent general community spread, according to the investigators.
In an accompanying editorial, Barnaby Flower, BMBS, and Christina Atchison, PhD, of the Department of Infectious Disease and School of Public Health, respectively, at Imperial College London in London, United Kingdom, lauded the study.
“Although general population estimates from dialysis sampling are imperfect, they at least remain consistent across the country and from one survey to the next, permitting longitudinal surveillance,” they wrote. “Despite the massive burden of COVID-19 in the USA, Anand and colleagues show that a small minority of the population has evidence of humoral immunity to SARS-CoV-2.”
Although questions remain with regard to the durability of the immune response and correlates of protection, Drs Flower and Atchison noted, high-quality longitudinal serosurveillance with accompanying clinical data can help to provide the answers.
“Anand and colleagues deserve credit for pioneering a scalable sampling strategy that offers a blueprint for standardised national serosurveillance in the USA and other countries with a large haemodialysing population,” they wrote.
Disclosure: This clinical trial was supported by Ascend Clinical Laboratories. Please see the original reference for a full list of authors’ disclosures.
Anand S, Montez-Rath M, Han J, et al. Prevalence of SARS-CoV-2 antibodies in a large nationwide sample of patients on dialysis in the USA: a cross-sectional study. Lancet. Published online September 25, 2020. doi:10.1016/S0140-6736(20)32009-2
Flower B, Atchison C. SARS-CoV-2 antibody seroprevalence in patients receiving dialysis in the USA. Lancet. Published online September 25, 2020. doi:10.1016/S0140-6736(20)32006-7
First nationally representative estimate of COVID-19 seroprevalence in the US suggests few in the population developed antibodies in the first wave [press release]. Lancet; September 25, 2020.