Cross-neutralization effect of the third dose of inactivated COVID-19 vaccine against the SARS-CoV-2 variants

Background The ongoing emergence of SARS-CoV-2 variants has raised concerns about the breadth of the immune response provided by existing vaccines.Research design and methods In this study, participants aged 18-75 years with no prior COVID-19 infection or vaccination history were enrolled to receive...

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Main Authors: Yuqing Li, Jiexiao He, Wenqing Liu, Runjie Qi, Jingxin Li, Fengcai Zhu
Format: Article
Language:English
Published: Taylor & Francis Group 2025-12-01
Series:Expert Review of Vaccines
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Online Access:https://www.tandfonline.com/doi/10.1080/14760584.2025.2550984
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Summary:Background The ongoing emergence of SARS-CoV-2 variants has raised concerns about the breadth of the immune response provided by existing vaccines.Research design and methods In this study, participants aged 18-75 years with no prior COVID-19 infection or vaccination history were enrolled to receive the CoronaVac vaccine. The interval between the first and second vaccine doses was 28 days, while the third dose was given 6 months after the second.Results Between February 1 to 15 February 2022, we recruited 40 eligible participants who had not received any COVID-19 vaccination and had no prior COVID-19 infection. After the third dose, neutralizing antibody levels significantly increased against the ancestral strain and certain Omicron variants (BA.1, BA.4/5, BF.7). Compared to levels observed 28 days post-second dose, neutralizing antibody levels rose further 28 days after the third dose, with the GMFI against the ancestral strain at 1.69 (95% CI: 1.27, 2.20). Among other variants, the GMFI against Omicron variants (BA.1, BA.4/5, BF.7) exceeded that for Beta and Delta, with the highest GMFI recorded for the BA.4/5 variant at 4.97 (95% CI: 3.08, 8.05).Conclusions The necessity of the third booster dose lies in its ability to enhance the breadth of the immune response.
ISSN:1476-0584
1744-8395