*Article* **Seroprevalence of Antibodies to SARS-CoV-2 in Guangdong Province, China between March to June 2020**

**Cheng Xiao 1,†, Nancy Hiu Lan Leung 2,†, Yating Cheng 3,4,†, Hui Lei 1, Shiman Ling 1, Xia Lin 1, Ran Tao 3,4, Xianzhong Huang 3,4, Wenda Guan 1, Zifeng Yang 1,5, Benjamin John Cowling 2, Mark Zanin 1,2 and Sook-San Wong 1,2,\***


**Abstract:** Guangdong province, located in South China, is an important economic hub with a large domestic migrant population and was among the earliest areas to report COVID-19 cases outside of Wuhan. We conducted a cross-sectional, age-stratified serosurvey to determine the seroprevalence of antibodies against SARS-CoV-2 after the emergence of COVID-19 in Guangdong. We tested 14,629 residual serum samples that were submitted for clinical testing from 21 prefectures between March and June 2020 for SARS-CoV-2 antibodies using a magnetic particle based chemiluminescent enzyme immunoassay and validated the results using a pseudovirus neutralization assay. We found 21 samples positive for SARS-CoV-2 IgG, resulting in an estimated age- and sex-weighted seroprevalence of 0.15% (95% CI: 0.06–0.24%). The overall age-specific seroprevalence was 0.07% (95% CI: 0.01–0.24%) in persons up to 9 years old, 0.22% (95% CI: 0.03–0.79%) in persons aged 10–19, 0.16% (95% CI: 0.07–0.33%) in persons aged 20–39, 0.13% (95% CI: 0.03–0.33%) in persons aged 40–59 and 0.18% (95% CI: 0.07–0.40%) in persons ≥60 years old. Fourteen (67%) samples had pseudovirus neutralization titers to S-protein, suggesting most of the IgG-positive samples were true-positives. Seroprevalence of antibodies to SARS-CoV-2 was low, indicating that there were no hidden epidemics during this period. Vaccination is urgently needed to increase population immunity to SARS-CoV-2.

**Keywords:** SARS-CoV-2; coronavirus disease 2019; seroprevalence; Guangdong; China; antibody
