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.

鉴于迄今为止血清学检测的可用性有限，不同人群中 SARS-CoV-2 特异性抗体的血清流行率仍不清楚。在这里，我们报告旧金山湾区两个人群中 SARS-CoV-2 血清阳性率非常低。 2020 年 4 月上旬，387 名因非呼吸系统疾病住院患者的血清反应性为 0.26%，1,000 名献血者的血清反应性为 0.1%。我们还描述了免疫球蛋白-G (IgG)、免疫球蛋白-M (IgM) 和体外的纵向动态。 COVID-19 患者的中和抗体滴度。这 3 项检测的血清转化中位时间为 10.3-11.0 天。症状出现后，中和抗体与免疫球蛋白滴度同步上升，IgG 检测与中和滴度之间的阳性一致性百分比 >93%。这些发现强调了在低流行人群中使用高精度检测进行监测研究的重要性，并提供证据表明使用 SARS-CoV-2 抗核衣壳蛋白 IgG 和抗尖峰 IgM 检测的血清反应性通常可以预测体外中和能力。