**1. Introduction**

Guangdong, located in South China, is the most populous province and an important economic hub of China. It has a population of 115 million and the largest economy in China [1]. The major economic and urban areas of Guangdong are centered around nine cities within the Pearl River Delta (PRD) that has a combined population of 63 million people. Due to its economic importance, 30% of its population consists of migrants from other provinces, making it the province with the most domestic migration in China [2]. Shenzhen and Guangzhou, both first-tier megalopolises in Guangdong, are major domestic and international transportation hubs and were among the earliest cities outside of Wuhan

**Citation:** Xiao, C.; Leung, N.H.L.; Cheng, Y.; Lei, H.; Ling, S.; Lin, X.; Tao, R.; Huang, X.; Guan, W.; Yang, Z.; et al. Seroprevalence of Antibodies to SARS-CoV-2 in Guangdong Province, China between March to June 2020. *Pathogens* **2021**, *10*, 1505. https:// doi.org/10.3390/pathogens10111505

Academic Editors: Philipp A. Ilinykh and Kai Huang

Received: 13 April 2021 Accepted: 13 May 2021 Published: 18 November 2021

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to report cases of COVID-19 [3,4]. Guangdong was also among the first provinces in China to declare a Level I public health emergency, the nation's highest emergency response level, on 23 January (Table S1) [5].

Seroprevalence studies have been used to inform the extent of transmission (including subclinical infections), herd immunity and the effectiveness of case-based surveillance in the community [6–8]. Given the importance of Guangdong as an economic, domestic migration and international transport hub, we investigated the community-wide SARS-CoV-2 virus transmission in Guangdong after the emergence of the virus, by conducting a cross-sectional seroprevalence study across province. Our aim was to estimate the agespecific seroprevalence of antibodies to SARS-CoV-2 in Guangdong province after the first wave of COVID-19 in China.
