Continuous population-level monitoring of SARS-CoV-2 seroprevalence in a large metropolitan region

Abstract

Serological assays can detect anti-SARS-CoV-2 (SARS2) antibodies, but their sensitivity often comes at the expense of specificity. Here we developed a Tripartite Automated Blood Immunoassay (TRABI) to assess the IgG response against SARS2. Calibration was per-formed with 90 prepandemic and 55 virologically and clinically confirmed COVID-19 sam-ples. Posterior probabilities of seropositivities were calculated from 3x8 measurements of logarithmically diluted samples against the ectodomain and the receptor-binding domain of the spike protein and the nucleoprotein. We then performed 760'320 assays on 5'503 prepandemic and 26'177 copandemic samples from hospital patients and healthy blood donors. We found 176 seropositive samples between December 2019 and May 2020. The seroprevalence increased conspicuously in March 2020 but plateaued in late April at 0.8-1.6% in both cohorts, indicating an equilibrium between new infections and the waning of immunity. This points to a high effectiveness of containment measures and/or to unex-pectedly rapid loss of humoral responses.

Performance characteristics of five immunoassays for SARS-CoV-2: a head-to-head benchmark comparison

“…Inconsistencies have been observed in the association between antibody titres and disease severity in other studies, which might relate to assay target. 20 , 24 , 25 Further studies definitively assessing the longer-term trajectory of antibodies in larger longitudinal cohorts of individuals with different disease severities and taking the specific assay type into account would be of benefit.…”

“…The Oxford immunoassay is an indirect ELISA, measuring serum IgG against trimeric spike protein, 19 using a horseradish peroxidase-linked anti-human IgG antibody as the secondary. We implemented this assay as previously described, 20 with minor modifications ( appendix p 10 ). Readouts were measured as a fluorescent signal, normalised to standard units by calibrating to a dilution series of the NHSBT controls and a monoclonal antibody (CR3022), using a natural cubic spline-based regression model to enable across-plate and across-batch comparisons ( appendix p 10 ).…”

Microfluidic Affinity Profiling reveals a Broad Range of Target Affinities for Anti-SARS-CoV-2 Antibodies in Plasma of COVID-19 Survivors

“…SARS-CoV-2 RBD, ACE2-receptor protein and SARS-CoV-2 spike S1 protein were purchased from SinoBio (Eschborn, DE). RBDs from SARS-CoV, HKU1, and OC43 were purified as outlined 1 . Microfluidic chips and cartridges for the measurements performed on the Fluidity One-W platform were provided by Fluidic Analytics (Cambridge, UK).…”

“…As part of a large-scale seroprevalence survey, plasma from over 10,000 healthy donors from the blood donation service (BDS) of the canton of Zurich was investigated for the presence of antibodies against SARS-CoV-2 Spike (S), receptor binding domain (RBD) and nucleocapsid proteins 1 .…”

“…However, the individual immune responses to any given virus are highly variable, and this can translate into different efficacies of viral clearance. Several studies have investigated antibodies generated during SARS-CoV-2 infection, thereby dissecting the antibody occurrence upon immune response [4][5][6][7][8] , antibody cross-reactivity 9 , disease prevalence in certain geographical areas 1,10,11 , and the temporal evolution of the antibody response on the population level 1,10,11 . Furthermore, multiple ongoing studies focus on the applicability of antibodies for therapeutic purposes 12 , including plasmapheresis [13][14][15][16][17] , which may be a promising therapeutic strategy 17 .…”