Objective

To elucidate the trend and clinical spectrum of virologically diagnosed varicella patients after implementation of universal vaccination as a national immunization program in Japan.

Patients and methods

Study subjects were patients suspected of varicella, less than 15 years of age, who visited 14 pediatric clinics in the Nagoya VZV Study Group from September 2015 to August 2019. Practitioners collected patient samples and information such as backgrounds, clinical symptoms, and previous immunization status. All patients were confirmed as having varicella based on molecular diagnostic assays.

Results

Varicella zoster virus (VZV) DNA was detected in swab samples from 506 (83.1%) of the 609 suspected patients. The 455 varicella patients for whom vaccination status was available were divided into two groups: 180 universal vaccination targets and 275 non-targets. Numbers of monthly varicella patients decreased gradually during the observation period. In the 2016/17 season, the seasonal epidemic of varicella became undetectable in the universal vaccination target group, and starting in the 2017/18 season, it was obscured even in the non-target group. The median age of patients was significantly lower in the universal vaccination target group (3 years) than the non-target group (7 years) (P < 0.001). Vaccination status differed significantly between the two groups (P < 0.001). Most varicella patients were in the non-target group, especially those who had been vaccinated once (60.4%). Frequency of fever (P < 0.001) and number of skin rashes at the time of the first hospital visit (P = 0.001) were significantly higher in the non-target group.

Conclusions

Although the number of childhood varicella patients declined after implementation of national immunization with two doses of varicella vaccination, sporadic outbreaks still occurred, mainly in the non–universal vaccination target group. Insufficient vaccination of members of this group is likely to be a major reason for small local outbreaks.

中文翻译：

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日本实施通用两剂水痘疫苗接种4年后水痘患者的趋势

目的

为了阐明在日本作为国家免疫计划实施普遍疫苗接种后，经病毒学诊断的水痘患者的趋势和临床范围。

患者和方法

研究对象为怀疑患有水痘的15岁以下患者，他们于2015年9月至2019年8月在名古屋VZV研究组的14家儿科诊所就诊。从业人员收集了患者样本以及诸如背景，临床症状和以前的免疫状况等信息。根据分子诊断分析，所有患者均被确认患有水痘。

结果

在609名可疑患者中，有506名（83.1％）的拭子样本中检出了水痘带状疱疹病毒（VZV）DNA。将455例可以接种疫苗的水痘患者分为两组：180例通用疫苗接种目标和275例非接种疫苗目标。在观察期内，每月的水痘患者数量逐渐减少。在2016/17赛季中，在通用疫苗接种目标人群中无法检测到水痘的季节性流行，从2017/18赛季开始，甚至在非目标人群中也将水痘的流行情况掩盖了。通用疫苗接种目标组（3岁）的患者中位年龄显着低于非目标疫苗接种组（7岁）（P  <0.001）。两组的疫苗接种状况差异显着（P <0.001）。大多数水痘患者属于非目标人群，尤其是曾经接种过一次水痘的人群（60.4％）。 在非目标人群 中，首次住院时的发烧频率（P <0.001）和皮疹数量（P = 0.001）显着更高。

结论

尽管在接受两次水痘疫苗全国免疫后，儿童水痘患者数量有所减少，但仍会零星爆发，主要发生在非普遍疫苗接种目标人群中。该组成员疫苗接种不足可能是局部小规模暴发的主要原因。