Estimated US Infection- and Vaccine-Induced SARS-CoV-2 Seroprevalence Based on Blood Donations, July 2020-May 2021

Abstract

IMPORTANCE People who have been infected with or vaccinated against SARS-CoV-2 have reduced risk of subsequent infection, but the proportion of people in the US with SARS-CoV-2 antibodies from infection or vaccination is uncertain.OBJECTIVE To estimate trends in SARS-CoV-2 seroprevalence related to infection and vaccination in the US population. DESIGN, SETTING, AND PARTICIPANTSIn a repeated cross-sectional study conducted each month during July 2020 through May 2021, 17 blood collection organizations with blood donations from all 50 US states; Washington, DC; and Puerto Rico were organized into 66 study-specific regions, representing a catchment of 74% of the US population. For each study region, specimens from a median of approximately 2000 blood donors were selected and tested each month; a total of 1 594 363 specimens were initially selected and tested. The final date of blood donation collection was May 31, 2021. EXPOSURE Calendar time.MAIN OUTCOMES AND MEASURES Proportion of persons with detectable SARS-CoV-2 spike and nucleocapsid antibodies. Seroprevalence was weighted for demographic differences between the blood donor sample and general population. Infection-induced seroprevalence was defined as the prevalence of the population with both spike and nucleocapsid antibodies. Combined infection-and vaccination-induced seroprevalence was defined as the prevalence of the population with spike antibodies. The seroprevalence estimates were compared with cumulative COVID-19 case report incidence rates. RESULTS Among 1 443 519 specimens included, 733 052 (50.8%) were from women, 174 842 (12.1%) were from persons aged 16 to 29 years, 292 258 (20.2%) were from persons aged 65 years and older, 36 654 (2.5%) were from non-Hispanic Black persons, and 88 773 (6.1%) were from Hispanic persons. The overall infection-induced SARS-CoV-2 seroprevalence estimate increased from 3.5% (95% CI, 3.2%-3.8%) in July 2020 to 20.2% (95% CI, 19.9%-20.6%) in May 2021; the combined infection-and vaccination-induced seroprevalence estimate in May 2021 was 83.3% (95% CI, 82.9%-83.7%). By May 2021, 2.1 SARS-CoV-2 infections (95% CI, 2.0-2.1) per reported COVID-19 case were estimated to have occurred. CONCLUSIONS AND RELEVANCEBased on a sample of blood donations in the US from July 2020 through May 2021, vaccine-and infection-induced SARS-CoV-2 seroprevalence increased over time and varied by age, race and ethnicity, and geographic region. Despite weighting to adjust for demographic differences, these findings from a national sample of blood donors may not be representative of the entire US population.

SARS-CoV-2 Neutralization in Convalescent Plasma and Commercial Lots of Plasma-Derived Immunoglobulin

“…The latter, which had an almost exponential increase with regards to ‘first-dose in’ in the total US population from January 2021 until May 2021, is potentially being responsible for the ongoing exponential increase in June 2021 [ 40 ]. This was also reported among blood donors where, with the onset of vaccinations in December 2020, an exponential increase was seen in overall seroprevalence to > 80% in May 2021, whilst infection-induced seroprevalence plateaued at that time [ 47 ].…”

“…The reported COVID-19 prevalence in July 2020 was about 1% [ 40 ], while recent reports suggest a 4.8-fold higher seroprevalence during the first wave of the pandemic [ 46 ]. In fact, a recent serological survey among US blood donors showed a 3.5% seroprevalence in July 2020 [ 47 ].…”

SARS-CoV-2 Neutralization in Convalescent Plasma and Commercial Lots of Plasma-derived Immunoglobulin

“…The latter which had an almost exponential increase with regards to "first-dose in" in the total US population from 01/2021 until 05/2021 is potentially being responsible for the ongoing exponential increase in 06/2021 [40]. This was also reported among blood donors where with the onset of vaccinations in 12/2020 an exponential increase was seen in overall seroprevalence to over 80% in May 2021, whilst infection-induced seroprevalence plateaued at that time [47].…”

“…Although the epidemiological comparison to the US total population [40] is a sub-optimal -yet easily availableindicator of vaccination and COVID-19 convalescence for the actual donor population [47] and given what we observe in individual IVIG lots, an increase in anti-SARS-CoV-2 antibody titer to meet trough levels suggested by Khoury and Cromer et al seems possible. The current maximum NC50 value measured in IVIG/SCIG was 864 IU/mL in 06/2021 and most seroconversions have occurred only recently (keeping in mind the >5-month lead time of IVIG/SCIG production).…”

“…The reported COVID-19 prevalence in 07/2020 was about 1% [40], while recent reports suggest a 4.8 fold higher seroprevalence during the first wave of the pandemic [46]. In fact a recent serological survey among US blood donors showed a 3.5% seroprevalence in July 2020 [47].…”