Study of efficacy and antibody duration to fourth-dose booster of Ad5-nCoV or inactivated SARS-CoV-2 vaccine in Chinese adults: a prospective cohort study

• Published in: Frontiers in immunology Vol. 14; p. 1244373
• Main Authors: Xu, Nani, Xu, Yu, Dai, Rongrong, Zheng, Lin, Qin, Pan, Wan, Peng, Yang, Yejing, Jiang, Jianmin, Zhang, Hangjie, Hu, Xiaowei, Lv, Huakun
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 06.09.2023
• Subjects: Ad5-nCoV; breakthrough infection; COVID-19; fourth dose; Immunology; SARS-CoV-2
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2023.1244373

Introduction China experienced a record surge of coronavirus disease 2019 cases in December 2022, during the pandemic. Methods We conducted a randomized, parallel-controlled prospective cohort study to evaluate efficacy and antibody duration after a fourth-dose booster with Ad5-nCoV or inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. Results A total of 191 participants aged ≥18 years who had completed a three-dose regimen of the inactivated SARS-CoV-2 vaccine 6 months earlier were recruited to receive the intramuscular Ad5-nCoV booster or the inactivated SARS-CoV-2 vaccine. The Ad5-nCoV group had significantly higher antibody levels compared with the inactivated vaccine group at 6 months after the fourth vaccination dose. After the pandemic, the breakthrough infection rate for the Ad5-nCoV and the inactivated vaccine groups was 77.89% and 78.13%, respectively. Survival curve analysis ( p = 0.872) and multivariable logistic regression analysis ( p = 0.956) showed no statistically significant differences in breakthrough infection between the two groups. Discussion Compared with a homologous fourth dose, a heterologous fourth dose of Ad5-nCoV elicited a higher immunogenic response in healthy adults who had been immunized with three doses of inactivated vaccine. Nevertheless, the efficacy of the two vaccine types was equivalent after the pandemic.