Jichi Medical University, Tochigi, Japan.
The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
JAMA Netw Open. 2022 Dec 1;5(12):e2247704. doi: 10.1001/jamanetworkopen.2022.47704.
Real-world evidence of SARS-CoV-2 transmission is needed to understand the prevalence of infection in the Japanese population.
To conduct sentinel screening of the Japanese population to determine the prevalence of SARS-CoV-2 infection in asymptomatic individuals, with complementary analysis for symptomatic patients as reported by active epidemiologic surveillance used by the government.
DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study of a sentinel screening program investigated approximately 1 million asymptomatic individuals with polymerase chain reaction (PCR) testing for SARS-CoV-2 infection between February 22 and December 8, 2021. Participants included children, students, employed adults, and older individuals, as well as volunteers to broadly reflect the general Japanese population in the 14 prefectures of Japan that declared a state of emergency. Saliva samples and a cycle threshold (Ct) value of approximately 40 as standard in Japan were used. Polymerase chain reaction testing for symptomatic patients was separately done by public health authorities, and the results were obtained from the Ministry of Health, Labour, and Welfare of Japan to complement data on asymptomatic infections from the present study.
Temporal trends in positivity and prevalence (including surges of different variants) and demographic associations (eg, age, geographic location, and vaccination status) were assessed.
The positive rate of SARS-CoV-2 infection in 1 082 976 asymptomatic individuals (52.08% males; mean [SD] age 39.4 [15.7] years) was 0.03% (95% CI, 0.02%-0.05%) during periods without surges and a maximum of 0.33% (95% CI, 0.25%-0.43%) during peak surges at the Japanese standard Ct value of approximately 40; however, the positive rate would have been 10-fold less at a Ct value of 25 as used elsewhere in the world (eg, UK). There was an increase in patients with a positive PCR test result with a Ct value of 25 or 30 preceding surges in infection and hotspots of asymptomatic infections.
In this cross-sectional study of asymptomatic SARS-CoV-2 infection in the general population of Japan in 2021, as investigated by sentinel surveillance, a low rate of infection was seen in the Japanese population compared with reported levels elsewhere in the world. This finding provides real-world data on the state of infection in Japan.
需要了解 SARS-CoV-2 在日本人群中的感染流行率，以获得真实世界的证据。
对日本人群进行哨点筛查，以确定无症状个体中 SARS-CoV-2 感染的流行率，并结合政府通过主动流行病学监测报告的有症状患者的补充分析。
设计、地点和参与者：这项关于哨点筛查计划的横断面研究调查了 2021 年 2 月 22 日至 12 月 8 日期间约 100 万无症状个体的 SARS-CoV-2 感染情况，这些个体接受了聚合酶链反应（PCR）检测。参与者包括儿童、学生、在职成年人和老年人，以及志愿者，以广泛反映日本 14 个宣布进入紧急状态的县的一般日本人群。日本使用的是唾液样本和大约 40 的循环阈值（Ct）值作为标准。对有症状患者的 PCR 检测由公共卫生当局单独进行，并从日本厚生劳动省获得结果，以补充本研究中无症状感染的数据。
评估了阳性率和流行率（包括不同变体的激增）的时间趋势以及人口统计学关联（例如，年龄、地理位置和疫苗接种状况）。
在没有激增的时期，1082976 名无症状个体（52.08%为男性；平均[标准差]年龄 39.4[15.7]岁）的 SARS-CoV-2 感染阳性率为 0.03%（95%CI，0.02%-0.05%），而在日本标准 Ct 值约为 40 的峰值激增期间，阳性率最高可达 0.33%（95%CI，0.25%-0.43%）；然而，如果使用世界其他地方（例如英国）使用的 Ct 值 25，则阳性率将低 10 倍。在感染和无症状感染热点地区之前，Ct 值为 25 或 30 的 PCR 检测阳性患者数量增加。
在 2021 年对日本普通人群进行的 SARS-CoV-2 无症状感染的这项横断面哨点监测研究中，与世界其他地区报告的水平相比，日本人群的感染率较低。这一发现提供了日本感染状况的真实世界数据。
