In the United States, cases of COVID-19, hospitalizations, and deaths overwhelmed health systems. More than 25 million cases of COVID-19 and more than 500,000 deaths have been attributed to SARS-CoV-2 infections. Nearly all regions of the country dealt with threats to their hospital capacity, with the largest numbers of cases occurring between November and December 2020.
Most persons infected with SARS-CoV-2, whether asymptomatic or symptomatic, mount a specific antibody response to the infection. SARS-CoV-2 receptor-binding domain (RBD) immunoglobin antibodies persist for at least 4 to 6 months after infections. Estimates of seroprevalence are an important measure of the extent of SARS-CoV-2 community spread.
Results of a previous study suggested that patients on dialysis could provide a sentinel population for SARS-CoV-2 seroepidemiology because patients have monthly laboratory testing that facilitate surveillance. The patient population includes older adults, members of racial/ethnic minority groups, and people from low-income settings.
Based on those results, Shuchi Anand, MD, and colleagues conducted a cross-sectional study to estimate seroprevalence of SARS-CoV-2 antibodies in patients receiving dialysis and in adults in the United States in January 2021, prior to widespread distribution of COVID-19 vaccines. Results of the study were reported online in JAMA Network Open [doi:10.1001/jamanetworkopen.2021.16572].
The study was conducted from January 1 to January 31, 2021, and utilized data from US Renal Care, the third largest dialysis organization in the United States. Remainder plasma from all patients receiving dialysis at US Renal Care facilities was tested for SARS-CoV-2 antibodies. Exclusion criteria were receipt of a documented dose of SARS-CoV-2 vaccination or a missing zip code in the electronic medical record.
The researchers standardized the crude seroprevalence estimates from the sample to the US adult population using 2018 American Community Survey 1-year estimates, stratified by age group, sex, self-reported race/ethnicity, neighborhood race/ethnicity composition, neighborhood income levels, and urban or rural status. The data and rates of case detection were compared with data from a July 2020 subsample of patients who received dialysis at the same facilities.
The spike protein RBD total antibody assay was used to estimate crude SARS-CoV-2 seroprevalence in the unweighted sample, and then the estimated seroprevalence rates for the US dialysis and adult populations were calculated, adjusted for age, sex, and region.
The study sample included 21,464 patients; mean age was 63.1 years, and 57% (n=12,265) were male. The patients were disproportionally older (65-79 years of age, 7847 [37%]; ≥80 years of age, 2668 [12%]) and members of racial/ethnic minority groups (Hispanic patients, 2945 [18%]; non-Hispanic Black patients, 4875 [29%]). Patients in 43 states were included in the sample; 33 states contributed ≥30 patients to the sample. There was modest overrepresentation from the South and West regions of the United States. Neighborhood race/ethnicity composition closely matched that of the US dialysis population.
In the unweighted sample of 21,464 patients, SARS-CoV-2 assay seroprevalence estimates in January 2021 were 18.9% (95% confidence interval [CI], 18.3%-19.5%), ranging from 15.3% in the Northeast to 20.8% in the South; 18.7% (95% CI, 18.1%-19.2%) standardized to the US dialysis population; and 21.3% (95% CI, 20.3%-22.3%) standardized to the US adult population. In the unweighted sample, the subgroups with the highest seroprevalence were younger age groups (18-44 years, 25.9%; 95% CI, 24.1%-27.8%), those who self-identified as Hispanic or living in Hispanic neighborhoods (25.1%; 95% CI, 23.6%-26.4%), and those living the lowest income neighborhoods (24.8%; 95% CI, 23.2%-26.5%).
Among patients within the US Renal Care network who underwent laboratory testing in July 2020, the unweighted sample SARS-CoV-2 seroprevalence rates were 4.4% (95% CI, 4.0%-4.8%), the dialysis-adjusted rates were 4.7% (95% CI, 4.3%-5.2%), and the US population-adjusted seroprevalence rates were 5.4% (95% CI, 4.6%-6.2%). Compared with those rates, the January 2021 seroprevalence rates were 1.8-fold higher in the Northeast, 4.1-fold higher in the Midwest, 5.1-fold higher in the West, and 5.1-fold higher in the South.
There was less variation in regional and rural versus urban seroprevalences than in the earlier study. The largest regional difference was 1.2-fold higher odds of seroprevalence in residents of the South in January 2021 compared with 2.3-fold higher odds of seroprevalence in residents in the Northeast versus the West in July 2020. Seroprevalence was 1.7-fold higher among those living in neighborhoods with a majority Hispanic population compared with neighborhoods with a majority White population, and 2.0-fold higher among those living in neighborhoods with ≥30% versus <10% of residents living at the federal poverty level.
Compared with data from July 2020, the estimated SARS-CoV-2 case detection rates increased from 14% to 23% in January 2021. Infection fatality rates decreased from 0.7% in July 2020 to 0.3% in January 2021.
In citing limitations to the study findings, the researchers included the lack of data on SARS-CoV-2 reverse transcriptase-polymerase chain reaction testing or COVID-19 symptoms, and the relative undersampling from the Northeast region of the United States. Because patients on dialysis are less likely to be employed and more likely to die from SARS-CoV-2 infections, SARS-CoV-2 seroprevalence in the general population may have been underestimated.
In conclusion, the authors said, “Results of this cross-sectional study suggest that, in the United States, fewer than one in four patients receiving dialysis and adults overall had evidence of SARS-CoV-2 antibodies in January 2021, which is well below the level needed to confer herd immunity. Residents of neighborhoods with a large population of racial/ethnic minority groups, those from low-income neighborhoods, and individuals from younger age groups had a substantially higher prevalence of SARS-CoV-2 antibodies. The results suggest that, because these subpopulations overlap with people who express high levels of vaccine hesitancy in the United States, vaccination campaigns may need to engage these high-risk groups to achieve sufficient penetration and reach community-level protection against SARS-CoV-2.”
- Researchers conducted a cross-sectional study to estimate the seroprevalence of SARS-CoV-2 antibodies in patients on dialysis and in the overall US adult population in January 2021, prior to the widespread introduction of COVID-19 vaccine.
- Seroprevalence of SARS-CoV-2 antibodies in a cohort of 21,464 patients who were receiving dialysis within US Renal Care was 18.9%, with a seroprevalence of 18.7% standardized to the US dialysis population, and 21.3% standardized to the US adult population.
- Younger persons, those who self-identified as Hispanic or living in Hispanic neighborhoods, and those living in the lowest-income neighborhoods were among the subgroups with the highest seroprevalence.