Evaluation of Immunogenicity by Pseudovirus Neutralization Assays for SARS‐CoV‐2 Variants after Primary and Booster Immunization. (April 2022)

• Record Type: Journal Article
• Authors: Xie, Hui; Wen, Xiaojing; Li, Juan; Chen, Weixin; Chen, Meng; Zhang, Lichi; Lv, Min; Zhou, Shanshan; Bai, Shuang; Zhao, Wei; Wang, Jian; Wu, Jiang
• Is Part Of: International journal of infectious diseases. Volume 117(2022)
• Page Start: 97
• Page End: 102
• Publication Date: 2022-04
• Subjects: SARS-CoV-2 variants -- Primary and booster immunization -- Pseudovirus neutralization assay -- Inactivated COVID-19 vaccine; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2022.01.068
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: A large-scale long-term prospective cohort study on inactivated COVID-19 vaccine. Two-dose inactivated vaccine induced the formation of neutralizing antibodies (NAbs). Memory-associated immune responses of inactivated vaccines were documented. High titers of NAbs against the variants obtained after booster immunization. Abstract: Objectives: To determine the status of immune responses after primary and booster immunization for SARS-CoV-2 variants and evaluate the differences in disease resistance based upon titers of neutralizing antibodies (NAbs) against the variants. Methods: Participants aged 18–59 years received 2 doses of inactivated COVID-19 vaccine, 14 days apart, and a booster dose after 12 months. Blood samples were collected before vaccination (baseline), 1 and 6 months after primary immunization, and at multiple instances within 21 days of the booster dose. NAbs against the spike protein of Wuhan-Hu-1 and 3 variants were measured using pseudovirus neutralization assays. Results: Of 400 enrolled participants, 387 completed visits scheduled within 6 months of the second dose and 346 participants received the booster dose in the follow-up research. After 1 month of primary immunization, geometric mean titers (GMTs) of NAbs peaked for Wuhan-Hu-1, whereas GMTs of other variants were <30. After 6 months of primary immunization, GMTs of NAbs against all strains were <30. After 3 days of booster immunization, GMTs were unaltered, seroconversion rates reached approximately 50% after 7 days, and GMTs of NAbs against all strains peaked at 14 days. Conclusion: Two-dose of inactivated COVID-19 vaccine induced the formation of NAbs and memory-associated immune responses, and high titers of NAbs against the variants obtained after booster immunization may further improve the effectiveness of the vaccine.