The overall goal of this proposal is to develop a new point-of-care test (POCT) —the D4-POCT— for serosurveillance of COVID-19 infection. The central hypothesis that underlies the proposal is that the D4 POCT will have the sensitivity of ELISA with the ease of use of lateral flow assays, enabling highly sensitive and user-friendly detection of host Abs generated against SARS-CoV-2. The specific objective is to develop two different formats of the D4-POCT to quantify host antibodies to SARS-CoV-2 — an indirect assay and a double antigen assay— and to compare their sensitivity and specificity with SARS-CoV-2 positive and negative blood and serum samples from infected and healthy individuals respectively. In Aim 1, we will develop a multiplexed indirect D4-POCT in which host generated antibodies against the S1 and N protein antigens of SARS-CoV-2 are captured by the two viral antigens that are printed as discrete spots on a “nonfouling”—protein- and cell-resistant — polymer brush on glass and then the captured host antibodies are subsequently labeled with an anti-human IgG/IgM secondary antibody that is also printed as soluble spots on the chip to determine isotype specific response. In Aim 2, we will develop a competing format, a multiplexed double antigen D4-POCT in which capture S1 and N antigens are inkjet printed as discrete spots on the chip and used to capture the host antibodies, followed by labeling with fluorescently labeled viral antigens that are printed as soluble spots on the chip. Unlike the indirect scheme, the double antigen D4-POCT detects total levels of SARS-COV-2 specific antibodies, which has been shown in some studies to be more sensitive than either IgG or IgM. In Aim 3, the analytical and clinical sensitivity and specificity will be compared for both POCTs. Clinical validation will be performed by testing 30 COVID-19 confirmed patient sera samples and 30 negative controls banked before the outbreak. If successful, this project will have a potentially transformative impact on COVID-19 testing and sero-surveillance. The COVID19 D4 POCT will be useful as an epidemiologic tool to estimate the disease burden more accurately, and as a research tool to correlate Ab responses with clinical outcome broadly and for cancer patients.