Effectiveness of Inactivated Vaccine against SARS-CoV-2 Delta Variant Infection in Xiamen, China—A Test-Negative Case-Control Study

Autor: Tingjuan He, Meixia Wang, Hongfei Mi, Liansheng Xu, Wenkui Lu, Xue Ouyang, Zhinan Guo, Chenghao Su
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Vaccines, Vol 11, Iss 3, p 532 (2023)
Druh dokumentu: article
ISSN: 2076-393X
DOI: 10.3390/vaccines11030532
Popis: Objective: Vaccine effectiveness can measure herd immunity, but the effectiveness of inactivated vaccines in Xiamen remains unclear. Our study was designed to understand the herd immunity of the COVID-19 inactivated vaccine against the SARA-CoV-2 Delta variant in the real world of Xiamen. Methods: We carried out a test-negative case-control study to explore the vaccine’s effectiveness. Participants aged over 12 years were recruited. A logistic regression was used to estimate the odds ratio (OR) of the vaccine among cases and controls. Results: This outbreak began with factory transmission clusters, and spread to families and communities during the incubation period. Sixty percent of cases were confirmed in a quarantine site. A huge mass of confirmed cases (94.49%) was identified within three days, and nearly half of them had a low Ct value. Following an adjustment for age and sex, a single dose of inactivated SARS-CoV-2 vaccine yielded the vaccine effectiveness (VE) of the overall case, of 57.01% (95% CI: −91.44~86.39%), the fully VE was 65.72% (95% CI: −48.69~88.63%) against COVID-19, 59.45% against moderate COVID-19 and 38.48% against severe COVID-19, respectively. The VE of fully vaccinated individuals was significantly higher in females than in males (73.99% vs. 46.26%). The VE among participants aged 19~40 and 41~61 years was 78.75% and 66.33%, respectively, which exceeds the WHO’s minimal threshold. Nevertheless, the VE in people under 18 and over 60 years was not observed because of the small sample size. Conclusions: The single-dose vaccine had limited effectiveness in preventing infection of the Delta variant. The two doses of inactivated vaccine could effectively prevent infection, and clinical mild, moderate, and severe illness caused by the SARS-CoV-2 Delta variant in people aged 18–60 years in the real world.
Databáze: Directory of Open Access Journals