Enhanced immunity against SARS-CoV-2 in returning Chinese individuals

• Published in: Human vaccines & immunotherapeutics Vol. 20; no. 1; p. 2300208
• Main Authors: Yuan, Runyu, Chen, Huimin, Yi, Lina, Li, Xinxin, Hu, Ximing, Li, Xing, Zhang, Huan, Zhou, Pingping, Liang, Chumin, Lin, Huifang, Zeng, Lilian, Zhuang, Xue, Ruan, QianQian, Chen, Yueling, Deng, Yingyin, Liu, Zhe, Lu, Jing, Xiao, Jianpeng, Chen, Liang, Xiao, Xincai, Li, Jing, Li, Baisheng, Li, Yan, He, Jianfeng, Sun, Jiufeng
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 31.12.2024; Taylor & Francis Group
• Subjects: Antibodies, Neutralizing; China - epidemiology; Coronavirus; COVID-19; COVID-19 - prevention & control; COVID-19 Vaccines; Humans; memory T-cell response; neutralizing antibody; Omicron; returning Chinese individuals; SARS-CoV-2; China; COVID-19; memory T-cell response; neutralizing antibody; SARS-CoV-2; Omicron; returning Chinese individuals
• ISSN: 2164-5515; 2164-554X; 2164-554X
• DOI: 10.1080/21645515.2023.2300208

Global COVID-19 vaccination programs effectively contained the fast spread of SARS-CoV-2. Characterizing the immunity status of returned populations will favor understanding the achievement of herd immunity and long-term management of COVID-19 in China. Individuals were recruited from 7 quarantine stations in Guangzhou, China. Blood and throat swab specimens were collected from participants, and their immunity status was determined through competitive ELISA, microneutralization assay and enzyme-linked FluoroSpot assay. A total of 272 subjects were involved in the questionnaire survey, of whom 235 (86.4%) were returning Chinese individuals and 37 (13.6%) were foreigners. Blood and throat swab specimens were collected from 108 returning Chinese individuals. Neutralizing antibodies against SARS-CoV-2 were detected in ~90% of returning Chinese individuals, either in the primary or the homologous and heterologous booster vaccination group. The serum NAb titers were significantly decreased against SARS-CoV-2 Omicron BA.5, BF.7, BQ.1 and XBB.1 compared with the prototype virus. However, memory T-cell responses, including specific IFN-γ and IL-2 responses, were not different in either group. Smoking, alcohol consumption, SARS-CoV-2 infection, COVID-19 vaccination, and the time interval between last vaccination and sampling were independent influencing factors for NAb titers against prototype SARS-CoV-2 and variants of concern. The vaccine dose was the unique common influencing factor for Omicron subvariants. Enhanced immunity against SARS-CoV-2 was established in returning Chinese individuals who were exposed to reinfection and vaccination. Domestic residents will benefit from booster homologous or heterologous COVID-19 vaccination after reopening of China, which is also useful against breakthrough infection.