Department of Nursing, Tokiwa University, Ibaraki, Japan.
National Institute of Infectious Diseases, Tokyo, Japan.
Drug Discov Ther. 2022;16(1):30-36. doi: 10.5582/ddt.2022.01000.
As of the end of November, 2021, the rate of completion for second-dose COVID-19 vaccine administration was almost 80% in Japan. We evaluated waning COVID-19 vaccine effectiveness in Japan, controlling for mutated strains, the Olympic Games, and countermeasures. The effective reproduction number R(t) was regressed on current vaccine coverage and data of a certain number of days prior, as well as shares of mutated strains, and an Olympic Games dummy variable along with data of temperature, humidity, mobility, and countermeasures. The study period was February, 2020 through November 4, as of November 25, 2021. Estimation results indicate that vaccine coverage of more than 90 days prior raises R(t) significantly. Especially, vaccine coverage with 90 or 120 days prior cancelled vaccine effectiveness completely. Results indicate significant waning of vaccine effectiveness from 90 days after the second dose.
截至 2021 年 11 月底，日本完成第二剂 COVID-19 疫苗接种的比例接近 80%。我们评估了日本 COVID-19 疫苗有效性的下降情况，同时控制了突变株、奥运会和对策的影响。有效繁殖数 R(t) 回归到当前的疫苗接种覆盖率和之前一定天数的数据，以及突变株的比例，以及奥运会哑变量以及温度、湿度、流动性和对策的数据。研究期间为 2020 年 2 月至 2021 年 11 月 4 日，截至 2021 年 11 月 25 日。估计结果表明，90 天前的疫苗接种覆盖率显著提高了 R(t)。特别是，90 天或 120 天前的疫苗接种覆盖率完全取消了疫苗的有效性。结果表明，第二剂疫苗接种后 90 天疫苗有效性显著下降。
