Use of US Blood Donors for National Serosurveillance of Severe Acute Respiratory Syndrome Coronavirus 2 Antibodies: Basis for an Expanded National Donor Serosurveillance Program

Abstract

Background: The Recipient Epidemiology and Donor Evaluation Study-IV-Pediatric (REDS-IV-P) Epidemiology, Surveillance and Preparedness of the Novel SARS-CoV-2 Epidemic (RESPONSE) seroprevalence study conducted monthly cross-sectional testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in blood donors in 6 US metropolitan regions to estimate the extent of SARS-CoV-2 infections over time.

Methods: During March-August 2020, approximately ≥1000 serum specimens were collected monthly from each region and tested for SARS-CoV-2 antibodies using a well-validated algorithm. Regional seroprevalence estimates were weighted based on demographic differences compared with the general population. Seroprevalence was compared with reported coronavirus disease 2019 (COVID-19) case rates over time.

Results: For all regions, seroprevalence was <1.0% in March 2020. New York, New York, experienced the biggest increase (peak seroprevalence, 15.8% in May). All other regions experienced modest increases in seroprevalence (1%-2% in May-June to 2%-4% in July-August). Seroprevalence was higher in younger, non-Hispanic black, and Hispanic donors. Temporal increases in donor seroprevalence correlated with reported case rates in each region. In August, 1.3-5.6 estimated cumulative infections (based on seroprevalence data) per COVID-19 case were reported to the Centers for Disease Control and Prevention.

Conclusions: Increases in seroprevalence were found in all regions, with the largest increase in New York. Seroprevalence was higher in non-Hispanic black and Hispanic than in non-Hispanic white blood donors. SARS-CoV-2 antibody testing of blood donor samples can be used to estimate the seroprevalence in the general population by region and demographic group. The methods derived from the RESPONSE seroprevalence study served as the basis for expanding SARS-CoV-2 seroprevalence surveillance to all 50 states and Puerto Rico.

Keywords: COVID-19; COVID-19 srological testing; SARS-CoV-2; seroprevalence.

Figure 1.

Flow charts of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serologic testing results for 6 US metropolitan regions. A, Parallel testing using the Roche Elecsys Nucleocapsid Anti-SARS-CoV-2 Total Immunoglobulin test (Elecsys CoV2T) and the pseudovirus reporter virus particle neutralization (RVPN) assay on samples reactive to the Ortho VITROS Immunodiagnostic Products Anti-SARS-CoV-2 Total test (Vitros CoV2T), collected during March–June 2020. B, Results from March–August 2020, combining the initial and revised supplementary testing algorithms. Abbreviations: NR, nonreactive; QNS, quantity not sufficient; R, reactive; S/CO, signal-to-cutoff ratio.

Figure 2.

Monthly distribution of all Ortho VITROS Immunodiagnostic Products Anti-SARS-CoV-2 Total test (Vitros CoV2T) values (A) and unadjusted and weighted cumulative seroprevalence (B), for 6 US metropolitan regions in March–August 2020. A, Red lines indicate the Vitros CoV2T signal-to-cutoff (S/CO) value for reactivity (S/CO ratio, 1.0; log₁₀ S/CO ratio, 0); black symbols, Black symbols, samples confirmed reactive based on the study algorithm; black lines, mean signal intensity of the Vitros CoV2T–reactive samples by region for each month of the study; gray symbols above the Vitros CoV2T cutoff threshold, samples that were reactive by the Vitros CoV2T screening assay but that were not confirmed using the study algorithm; gray symbols below the red line, samples that were nonreactive with the Vitros CoV2T assay; open black symbol (Seattle panel, June column), the only sample with Vitros CoV2T signal-to-cutoff ratio (S/CO) >10 that was not confirmed. Numbers represent number of sampled donations for each month. B, Screened and confirmed seroprevalence for each region, and confirmed seroprevalence restricted to zip code of residence.

Figure 3.

Weighted confirmed severe acute respiratory syndrome coronavirus 2 seroprevalence derived from blood donors, coronavirus disease 2019 (COVID-19) case rates per 100 000 population (reported to the Centers for Disease Control and Prevention [CDC]), and daily COVID-19 case rates per 100 000 (as reported to the CDC) in 6 US metropolitan regions, March–August 2020.