Wang Kai, Zeng Ting, Guo Zihao, Liang Jing, Sun Shengzhi, Ni Yongkang, Yan Chunyan, Yin Liang, Wang Lan, Li Hui, Wang Kailu, Chong Marc K C, Tang Naijun, Dai Jianghong, Luo Zhaohui, Zhao Shi
Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi, 830017, China.
JC School of Public Health and Primary Care, Chinese University of Hong Kong, Hong Kong, 999077, China.
BMC Infect Dis. 2024 Dec 18;24(1):1401. doi: 10.1186/s12879-024-10250-1.
After the exit "zero-COVID" strategy in mainland China by the end of 2022, a large-scale COVID-19 outbreak seeded by Omicron variants occurred. An inhaled adenovirus type-5 vector-based (i.e., inhaled Ad5-nCoV) COVID-19 vaccine was licensed earlier in 2021. In this study, we aimed to assess the real-world effectiveness of a heterologous booster of inhaled Ad5-nCoV vaccine against Omicron infection and compared with the protection from hybrid immunity (i.e., prior breakthrough infection).
In this retrospective cohort study, we identified 1087 out of a total of 1146 hospital staff from a tertiary hospital in Urumqi city, China from November 22 to December 29, 2022. Demographic characteristics, baseline health status, occupation, behavioral factors, laboratory test of serological IgG antibody, and timeline from immunization to laboratory-testing outcome were obtained. We analysed the individual-level vaccination status of inhaled Ad5-nCoV vaccine, prior SARS-CoV-2 infection status and baseline vaccination status, and other risk factors before follow-up. The protective effects of the heterologous inhaled Ad5-nCoV vaccine and hybrid immunity against Omicron BA.5 infection and hospitalization were calculated as relative rate reduction (RRR), which was estimated using multivariate Poisson regression models.
A total of 1087 hospital staff (median age of 34 years, and 343 males [31.6%]), including 931 accepted for serological antibody tests, were recruited to assess the vaccine effectiveness (VE) of the inhaled Ad5-nCoV booster and hybrid immunity. Among the 1087 participants, 413 had a history of prior SARS-CoV-2 infection (before follow-up) but did not receive an inhaled Ad5-nCoV booster, and 674 reported no prior infection, including 390 who received an inhaled Ad5-nCoV booster. The highest serological IgG antibody level was detected among the inhaled Ad5-nCoV group, with a median of 294.59 S/CO, followed by the hybrid immunity group, with a median of 93.65 S/CO compared to the reference level of the inactivated vaccine group (most of whom received the Sinopharm/BBIBP-CorV vaccine). The inhaled Ad5-nCoV booster and hybrid immunity yielded RRRs of 41.9% (95% CI: 24.8, 55.0) and 97.9% (95% CI: 94.2, 99.2), respectively, against Omicron BA.5 infection, regardless of symptom status.
We found that hybrid immunity could provide a high level of protection against Omicron infection, while a heterologous inhaled Ad5-nCoV booster conferred a moderate level of protection. Our findings supported the rollout of a heterologous vaccination strategy regardless of preexisting vaccine coverage.
2022年底中国大陆实施“动态清零”政策后，由奥密克戎变异株引发了大规模新冠疫情。一种基于5型腺病毒载体的吸入式新冠疫苗（即吸入用Ad5-nCoV）于2021年早些时候获批上市。在本研究中，我们旨在评估吸入用Ad5-nCoV疫苗异源加强针预防奥密克戎感染的真实世界有效性，并与混合免疫（即既往突破性感染）的保护效果进行比较。
在这项回顾性队列研究中，我们从中国乌鲁木齐市一家三级医院的1146名医院工作人员中，确定了1087名作为研究对象，研究时间为2022年11月22日至12月29日。收集了人口统计学特征、基线健康状况、职业、行为因素、血清IgG抗体实验室检测结果以及从免疫接种到实验室检测结果的时间线等信息。我们分析了吸入用Ad5-nCoV疫苗的个体接种状态、既往SARS-CoV-2感染状态和基线接种状态，以及随访前的其他风险因素。采用多变量泊松回归模型估计异源吸入用Ad5-nCoV疫苗和混合免疫对奥密克戎BA.5感染和住院的保护效果，以相对风险降低率（RRR）表示。
共招募了1087名医院工作人员（中位年龄34岁，男性343名[31.6%]），其中931名接受了血清抗体检测，以评估吸入用Ad5-nCoV加强针和混合免疫的疫苗有效性（VE）。在1087名参与者中，413人有既往SARS-CoV-2感染史（随访前）但未接受吸入用Ad5-nCoV加强针，674人报告无既往感染，其中390人接受了吸入用Ad5-nCoV加强针。吸入用Ad5-nCoV组的血清IgG抗体水平最高，中位数为294.59 S/CO，其次是混合免疫组，中位数为93.65 S/CO，而灭活疫苗组（大多数接种的是国药集团/BBIBP-CorV疫苗）的参考水平最低。无论症状状态如何，吸入用Ad5-nCoV加强针和混合免疫对奥密克戎BA.5感染的RRR分别为41.9%（95%CI：24.8，55.0）和97.9%（95%CI：94.2，99.2）。
我们发现混合免疫可提供高水平的保护以预防奥密克戎感染，而异源吸入用Ad5-nCoV加强针可提供中等水平的保护。我们的研究结果支持无论现有疫苗接种覆盖率如何，都应推行异源疫苗接种策略。
