Effectiveness of COVID-19 vaccines against infection in Japan: A test-negative study from the VENUS study

• Published in: Vaccine Vol. 41; no. 37; pp. 5447 - 5453
• Main Authors: Tamada, Yudai, Takeuchi, Kenji, Kusama, Taro, Maeda, Megumi, Murata, Fumiko, Osaka, Ken, Fukuda, Haruhisa
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 23.08.2023; Elsevier Limited
• Subjects: Age groups; B.1.617.2; Clinical trials; Comorbidity; Coronaviruses; COVID-19; COVID-19 diagnostic tests; COVID-19 vaccines; Effectiveness; Epidemics; Health care facilities; Health care policy; Infections; Infectious diseases; Older people; Public health; Regression analysis; SARS-CoV-2; Statistical analysis; Test-negative; Trends; Vaccination; Vaccines; Variants of concern; Viral diseases; Japan; Variants of concern; SARS-CoV-2; B.1.617.2; Vaccination; Test-negative
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2023.07.035

•This is the first multi-region community-based test-negative study in Japan.•High real-world effectiveness of COVID-19 vaccines against infection was observed.•The vaccines effectiveness at ≥14 days after the second dose was found to be ≥80%. Although the effectiveness of coronavirus disease 2019 (COVID-19) vaccines is a crucial public health concern, evidence from Western Pacific countries is limited, including Japan. This study aimed to estimate the COVID-19 vaccines effectiveness (VE) against infection during the Delta variant predominance (July–September 2021) in Japan. We performed a test-negative study using COVID-19 test data of ≥20-year-old residents in four municipalities who were tested in medical institutions between July 1 and September 30, 2021. We extracted COVID-19 test data from healthcare claims data, and the vaccination status at the testing date was ascertained using the Vaccination Record System data. Confirmed positive cases were identified using data from the national system for COVID-19, Health Center Real-time Information-sharing System on COVID-19. Logistic regression analyses were conducted to estimate the odds of testing positive according to vaccination status. VE was calculated as (1 − odds ratio) × 100%. This study included 530 positive and 15,650 negative results. Adjusted manufacturer-unspecified VE was 4.1% (95% confidence interval [CI], −36.5–32.6) at 0–13 days after the first dose, 45.2% (95% CI, 13.4–65.3) at ≥14 days after the first dose, 85.2% (95% CI, 69.9–92.7) at 0–13 days after the second dose, and 79.6% (95% CI, 72.6–84.8) at ≥14 days after the second dose. In addition, the VE after the second dose was highest at 14–34 days after the dose (VE, 89.1%; 95% CI, 80.5–93.9). High real-world effectiveness of COVID-19 vaccines, especially two doses, against infection during the Delta variant predominance in Japan was confirmed.