Department of Education and Support for Regional Medicine, Tohoku University, Seiryo-machi 1-1, Aoba-ku, Sendai, Miyagi, 980-8574, Japan.
Division of Emergency and Critical Care Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
Sci Rep. 2022 Aug 10;12(1):13589. doi: 10.1038/s41598-022-17990-7.
The administration of a third booster dose of messenger ribonucleic acid (mRNA) vaccines against coronavirus disease 2019 (COVID-19) has progressed worldwide. Since January 2022, Japan has faced a nationwide outbreak caused by the Omicron variant, which occurred simultaneously with the progression of mass vaccination with the third booster dose. Therefore, this study evaluated the effectiveness of the third dose of vaccine by reverse transcription-polymerase chain reaction (RT-PCR) test using nasopharyngeal swab samples from adults aged ≥ 18 years tested after having close contact with COVID-19 cases between January and May 2022. Participants who completed only one dose were excluded from the study. Among the 928 enrolled participants, 139 had never been vaccinated, 609 had completed two doses, 180 had completed three doses before the swab test, and the overall RT-PCR test positivity rate in each group was 48.9%, 46.0%, and 32.2%, respectively. The vaccine effectiveness of the third dose to prevent infection after close contact was approximately 40% (95% confidence interval: 20-60%), which was the highest at 10-70 days after receiving the third dose. In conclusion, the effectiveness of the three-dose mRNA COVID-19 vaccine after close contact during the Omicron outbreak is approximately 40%.
全球范围内已经开始管理第三次信使核糖核酸（mRNA）疫苗接种以预防 2019 年冠状病毒病（COVID-19）。自 2022 年 1 月以来，日本面临着由奥密克戎变异株引起的全国性疫情，该疫情与第三次加强针大规模接种同时发生。因此，本研究通过对 2022 年 1 月至 5 月期间与 COVID-19 病例有密切接触的成年人进行鼻咽拭子样本的逆转录-聚合酶链反应（RT-PCR）检测，评估了第三剂疫苗的有效性。研究排除了仅接种一剂疫苗的参与者。在 928 名入组参与者中，有 139 人从未接种过疫苗，609 人完成了两剂接种，180 人在接受拭子检测前完成了三剂接种，每组的总体 RT-PCR 检测阳性率分别为 48.9%、46.0%和 32.2%。第三剂疫苗对密切接触后感染的预防效果约为 40%（95%置信区间：20-60%），在接种第三剂后 10-70 天效果最高。综上所述，在奥密克戎疫情期间，密切接触后三剂 mRNA COVID-19 疫苗的有效性约为 40%。
