Rubella remains a public health challenge in Japan, impeding the attainment of herd immunity. Despite vaccination efforts since 1976, persistent outbreaks reveal a susceptibility gap in male adults born before 1995. Seroepidemiological surveys are pivotal in evaluating population immunity and identifying at-risk groups. This study aims to pinpoint high-risk areas for potential rubella outbreaks in Japan by merging seroepidemiological data from 2020 with population census information. Various data sources, including spatial demographic data, reported rubella and congenital rubella syndrome (CRS) cases, and traveler lodging statistics, were employed. Geospatial information for Japan's 230,300 small geographic areas was analyzed, and HI (hemagglutination inhibition) titers were examined by age and sex. Seroconversion was defined as an HI titer ≥ 1:32 or 1:16, indicating protective immunity. Geospatial maps illustrated the distribution of susceptible individuals per square kilometer, emphasizing high-risk urban areas like Tokyo and Osaka. Demographic shifts in the working-age population were assessed. Susceptible individuals cluster in densely populated urban centers, persisting despite demographic changes. The study highlights areas at risk of increased susceptibility, particularly with an HI titer cut-off of 1:16. Foreign travelers pose potential rubella importation risks as travel volume to Japan rises. To prevent epidemics and congenital rubella syndrome burden, achieving and sustaining herd immunity in high-risk areas is crucial. This study offers a comprehensive assessment of vulnerability in densely populated Japanese regions. Integrating population statistics with seroepidemiological data enhances our understanding of population immunity, guiding resource allocation for supplementary vaccination planning. To avert rubella epidemics, high-risk locations must bolster indirect protection through herd immunity, ultimately preventing congenital rubella syndrome.

中文翻译：

---

确定 2020 年日本风疹易感人群：精细风险图谱

风疹仍然是日本的一个公共卫生挑战，阻碍了群体免疫的实现。尽管自 1976 年以来一直在努力开展疫苗接种工作，但持续的疫情暴发揭示了 1995 年之前出生的男性成年人之间存在易感性差距。血清流行病学调查对于评估人群免疫力和识别高危人群至关重要。本研究旨在通过将 2020 年的血清流行病学数据与人口普查信息相结合，查明日本潜在风疹疫情的高风险地区。采用了各种数据源，包括空间人口统计数据、报告的风疹和先天性风疹综合征（CRS）病例以及旅行者住宿统计数据。对日本 230,300 个小地理区域的地理空间信息进行了分析，并按年龄和性别检查了 HI（血凝抑制）滴度。血清转化定义为 HI 滴度 ≥ 1:32 或 1:16，表明有保护性免疫力。地理空间地图显示了每平方公里易感人群的分布情况，强调了东京和大阪等高风险城市地区。对劳动年龄人口的人口变化进行了评估。易感人群聚集在人口稠密的城市中心，尽管人口结构发生变化，但这些人群仍然存在。该研究强调了易感性增加风险的区域，特别是 HI 滴度截止值为 1:16 的区域。随着前往日本的旅游量增加，外国游客构成潜在的风疹输入风险。为了预防流行病和先天性风疹综合症负担，在高风险地区实现和维持群体免疫至关重要。这项研究对日本人口稠密地区的脆弱性进行了全面评估。将人口统计数据与血清流行病学数据相结合可以增强我们对人口免疫的理解，指导补充疫苗接种计划的资源分配。为了避免风疹流行，高风险地区必须通过群体免疫加强间接保护，最终预防先天性风疹综合症。