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

ABSTRACT

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.

KEYWORDS:

• COVID-19
• SARS-CoV-2
• returning Chinese individuals
• Omicron
• neutralizing antibody
• memory T-cell response

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

S.J., H.J., L.Y., L.B. and L.J. designed the study. Y.R., C.H., Y.L., Z.H., Z.P., L.C., L.H., Z.L., Z.X., R.Q. and H.X. all contributed to the experimental part of the study. L.X., C.Y., D.Y., L.Z., L.J., X.J. and X.X. contributed to data analysis. C.H. and L.X. drafted the manuscript, and S.J. and Y.R. revised the final manuscript. All authors contributed to data acquisition and data interpretation and reviewed and approved the final version.

Supplementary Material

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2023.2300208.

Additional information

Funding

This work was supported by grants from the Guangdong Science and Technology Program [2022A1111090004, 2021B1212030007, 2021A0505110014].