Kusabue Nursery School, Tokyo, Japan.
National Institute of Infectious Diseases, Tokyo, Japan.
Vaccine. 2024 Apr 11;42(10):2637-2645. doi: 10.1016/j.vaccine.2024.02.075. Epub 2024 Mar 13.
In Japan, routine administration to one-year-old children of two-dose immunization for varicella was introduced in October 2014. Object The object of this study was to report outbreaks of varicella under routine immunization at a nursery school and in its surrounding area using data of surrounding areas from the (Nursery) School Absenteeism Surveillance System. Then, we measured the effectiveness of routine two-dose immunization for varicella to onset. We tentatively assessed its severity in a nursery school.
The study period extended from April 2017 through March 2018. The study area comprised Nursery school B and other nursery schools, and elementary and junior high schools in City A. Subjects in Nursery school B were 120 children. We analyzed vaccine effectiveness (VE) as an observational study and assessed severity using Fisher's exact test. We also assessed VE for severity using linear regression. Severity was defined as the length of nursery school absence attributable to varicella infection.
During the one month preceding a period of two weeks before the initial case at Nursery school B, there were 16 cases of varicella infection in nursery schools, 45 cases in elementary schools, and one case in junior high schools in City A. For children who had received one vaccine dose or more, VE was 48.1% for all ages and 49.2% among children three years old and older. No significant VE against infection was found. Vaccination using one dose or more can reduce severity significantly.
Because many nursery school children who had received two doses of vaccine were infected, VE was estimated as low in the nursery school and not significant. Although VE for severity with more than one dose was confirmed, a second dose might not reduce severity compared to one dose.
在日本，自 2014 年 10 月起，为一岁儿童常规接种两剂水痘疫苗。目的本研究旨在利用周边地区（幼儿园）缺勤监测系统的数据，报告幼儿园及其周边地区常规免疫接种下的水痘暴发情况。然后，我们测量了常规两剂水痘疫苗预防发病的效果。我们初步评估了幼儿园的严重程度。
研究期从 2017 年 4 月至 2018 年 3 月。研究区域包括幼儿园 B 及其他幼儿园、市 A 的小学和初中。幼儿园 B 的研究对象为 120 名儿童。我们将疫苗有效性（VE）作为一项观察性研究进行分析，并使用 Fisher 精确检验评估严重程度。我们还使用线性回归评估严重程度的 VE。严重程度定义为因水痘感染而缺勤的幼儿园天数。
在幼儿园 B 的首例病例前两周的一个月内，该市的幼儿园有 16 例水痘感染，小学有 45 例，初中有 1 例。对于接种了一剂或多剂疫苗的儿童，所有年龄组的 VE 为 48.1%，3 岁及以上儿童的 VE 为 49.2%。未发现对感染有显著的 VE。接种一剂或多剂疫苗可显著降低严重程度。
由于许多接种了两剂疫苗的幼儿园儿童都被感染，因此在幼儿园中 VE 估计较低，且不显著。尽管证实了一剂以上疫苗对严重程度的 VE，但与一剂相比，第二剂可能不会降低严重程度。
