SARS-CoV-2 seroprevalence and neutralizing activity in donor and patient blood

Ng, Dianna L.; Goldgof, Gregory M.; Shy, Brian R.; Levine, Andrew G.; Balcerek, Joanna; Bapat, Sagar P.; Prostko, John; Rodgers, Mary; Coller, Kelly; Pearce, Sandra; Franz, Sergej; Du, Li; Stone, Mars; Pillai, Satish K.; Sotomayor-Gonzalez, Alicia; Servellita, Venice; Martin, Claudia Sanchez San; Granados, Andrea; Glasner, Dustin R.; Han, Lucy M.; Truong, Kent; Akagi, Naomi; Nguyen, David N.; Neumann, Neil M.; Qazi, Daniel; Hsu, Elaine; Gu, Wei; Santos, Yale A.; Custer, Brian; Green, Valerie; Williamson, Phillip; Hills, Nancy K.; Lu, Chuanyi M.; Whitman, Jeffrey D.; Stramer, Susan L.; Wang, Candace; Reyes, Kevin; Hakim, Jill M. C.; Sujishi, Kirk; Alazzeh, Fariba; Pham, Lori; Thornborrow, Edward; Oon, Ching-Ying; Miller, Steve; Kurtz, Theodore; Simmons, Graham; Hackett, John; Busch, Michael P.; Chiu, Charles Y.

Given the limited availability of serological testing to date, the seroprevalence of SARS-CoV-2-specific antibodies in different populations has remained unclear. Here, we report very low SARS-CoV-2 seroprevalence in two San Francisco Bay Area populations. Seroreactivity was 0.26% in 387 hospitalized patients admitted for non-respiratory indications and 0.1% in 1,000 blood donors in early April 2020. We additionally describe the longitudinal dynamics of immunoglobulin-G (IgG), immunoglobulin-M (IgM), and in vitro neutralizing antibody titers in COVID-19 patients. The median time to seroconversion ranged from 10.3–11.0 days for these 3 assays. Neutralizing antibodies rose in tandem with immunoglobulin titers following symptom onset, and positive percent agreement between detection of IgG and neutralizing titers was >93%. These findings emphasize the importance of using highly accurate tests for surveillance studies in low-prevalence populations, and provide evidence that seroreactivity using SARS-CoV-2 anti-nucleocapsid protein IgG and anti-spike IgM assays are generally predictive of in vitro neutralizing capacity.