ABSTRACT The effectiveness of inactivated SARS-CoV-2 vaccines against the Delta variant, which has been associated with greater transmissibility and virulence, remains unclear. We conducted a test-negative case–control study to explore the vaccine effectiveness (VE) in real-world settings. We recruited participants aged 18–59 years who consisted of SARS-CoV-2 test-positive cases ( n = 74) and test-negative controls ( n = 292) during the outbreak of the Delta variant in May 2021 in Guangzhou city, China. Vaccination status was compared to estimate The VE of SARS-CoV-2 inactivated vaccines. A single dose of inactivated SARS-CoV-2 vaccine yielded the VE of only 13.8%. After adjusting for age and sex, the overall VE for two-dose vaccination was 59.0% (95% confidence interval: 16.0% to 81.6%) against coronavirus disease 2019 (COVID-19) and 70.2% (95% confidence interval: 29.6–89.3%) against moderate COVID-19 and 100% against severe COVID-19 which might be overestimated due to the small sample size. The VE of two-dose vaccination against COVID-19 reached 72.5% among participants aged 40–59 years, and was higher in females than in males against COVID-19 and moderate diseases. While single dose vaccination was not sufficiently protective, the two-dose dosing scheme of the inactivated vaccines was effective against the Delta variant infection in real-world settings, with the estimated efficacy exceeding the World Health Organization minimal threshold of 50%.
【저자키워드】 SARS-CoV-2, Coronavirus disease 2019, Vaccine, delta variant, efficacy of vaccination, 【초록키워드】 COVID-19, coronavirus disease, Coronavirus disease 2019, Efficacy, vaccination, Diseases, Inactivated Vaccines, severe COVID-19, Infection, delta variant, SARS-CoV-2 vaccine, Moderate COVID-19, China, Inactivated vaccine, outbreak, male, female, Effectiveness, Control, threshold, virulence, moderate, inactivated, single dose, Protective, Guangzhou, Health Organization, Vaccination Status, World Health Organization, 95% confidence interval, participant, small sample size, while, greater transmissibility, vaccination against COVID-19, effective, recruited, conducted, reached, the vaccine, age and sex, 【제목키워드】 Infection, SARS-CoV-2 vaccine, inactivated,