Trend in varicella patients 4 years after implementation of universal two-dose varicella vaccination in Japan

Fumihiko Hattori; Kei Kozawa; Hiroki Miura; Yoshiki Kawamura; Yuki Higashimoto; Akiko Yoshikawa; Masaru Ihira; Tetsushi Yoshikawa; Nagoya VZV Study Group

doi:10.1016/j.vaccine.2020.09.038

Trend in varicella patients 4 years after implementation of universal two-dose varicella vaccination in Japan

Vaccine. 2020 Oct 27;38(46):7331-7336. doi: 10.1016/j.vaccine.2020.09.038. Epub 2020 Sep 30.

Authors

Fumihiko Hattori¹, Kei Kozawa², Hiroki Miura², Yoshiki Kawamura², Yuki Higashimoto³, Akiko Yoshikawa², Masaru Ihira⁴, Tetsushi Yoshikawa²; Nagoya VZV Study Group

Affiliations

¹ Department of Pediatrics, Kariya Toyota General Hospital, Kariya, Aichi 448-8505, Japan; Department of Pediatrics, Fujita Health University School of Medicine, Toyoake, Aichi, Japan. Electronic address: kuma2315@outlook.jp.
² Department of Pediatrics, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
³ Faculty of Medical Technology, Fujita Health University School of Medical Sciences, Toyoake, Aichi, Japan.
⁴ Faculty of Clinical Engineering, Fujita Health University School of Medical Sciences, Toyoake, Aichi, Japan.

PMID: 33008671
DOI: 10.1016/j.vaccine.2020.09.038

Abstract

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.

Keywords: Catch-up immunization; Universal immunization; Varicella.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Chickenpox Vaccine
Chickenpox* / epidemiology
Chickenpox* / prevention & control
Child
Child, Preschool
Herpes Zoster*
Herpesvirus 3, Human
Humans
Japan / epidemiology
Vaccination

Substances

Chickenpox Vaccine