Kyoto University School of Public Health, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8601, Japan.
Math Biosci Eng. 2024 Sep 12;21(9):7087-7101. doi: 10.3934/mbe.2024312.
Clusters of COVID-19 in high-risk settings, such as schools, have been deemed a critical driving force of the major epidemic waves at the societal level. In Japan, the vaccination coverage among students remained low up to early 2022, especially for 5-11-year-olds. The vaccination of the student population only started in February 2022. Given this background and considering that vaccine effectiveness against school transmission has not been intensively studied, this paper proposes a mathematical model that links the occurrence of clustering to the case count among populations aged 0-19, 20-59, and 60+ years of age. We first estimated the protected (immune) fraction of each age group either by infection or vaccination and then linked the case count in each age group to the number of clusters via a time series regression model that accounts for the time-varying hazard of clustering per infector. From January 3 to May 30, 2022, there were 4,722 reported clusters in school settings. Our model suggests that the immunity offered by vaccination averted 226 (95% credible interval: 219-232) school clusters. Counterfactual scenarios assuming elevated vaccination coverage with faster roll-out reveal that additional school clusters could have been averted. Our study indicates that even relatively low vaccination coverage among students could substantially lower the risk of clustering through vaccine-induced immunity. Our results also suggest that antigenically updated vaccines that are more effective against the variant responsible for the ongoing epidemic may greatly help decrease not only the incidence but also the unnecessary loss of learning opportunities among school-age students.
在高风险环境（如学校）中出现的 COVID-19 集群被认为是社会层面重大疫情浪潮的关键驱动因素。在日本，直到 2022 年初，学生的疫苗接种率仍然很低，尤其是 5-11 岁的儿童。学生群体的疫苗接种仅在 2022 年 2 月开始。鉴于这种背景，并且考虑到针对学校传播的疫苗有效性尚未得到深入研究，本文提出了一个数学模型，将集群的发生与 0-19 岁、20-59 岁和 60 岁以上人群的病例数联系起来。我们首先通过感染或接种来估计每个年龄组的保护（免疫）比例，然后通过时间序列回归模型将每个年龄组的病例数与集群数量联系起来，该模型考虑了每个感染者的集群时间变化风险。从 2022 年 1 月 3 日至 5 月 30 日，学校环境中报告了 4722 个集群。我们的模型表明，疫苗提供的免疫力避免了 226 个（95%可信区间：219-232）学校集群。假设疫苗接种覆盖率提高且推出速度加快的反事实情景表明，可能会避免更多的学校集群。我们的研究表明，即使学生的疫苗接种率相对较低，通过疫苗诱导的免疫力也可以大大降低集群的风险。我们的研究结果还表明，针对导致当前疫情的变异体更有效的抗原更新疫苗可能会极大地帮助减少不仅是发病率，还有学龄学生不必要的学习机会损失。
