New nanoimmunoassay can detect anti–SARS-CoV-2 antibodies in ultralow-volume blood samples The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been the largest global public health crisis in recent memory. To date, it has been responsible for over 158.3 million infections and over 3.3 million deaths the world over. Managing this crisis, mitigating viral spread, and planning to prepare for the next phase of the pandemic involves numerous testing and analysis regimes. Continuous monitoring of the virus spread to control the disease, the efficacy of vaccines in trials, current infection fatality rates and the health status post-vaccination, call for a large sampling of blood and tests to detect the seroprevalence of SARS-CoV-2.