Varicella‐Zoster Virus Clades Circulating Among Children With Varicella and Adults With Central Nervous System Infection in Japan

Varicella‐zoster virus (VZV) causes varicella in children, establishes lifelong latency and reactivates to cause herpes zoster later in life. Implementation of routine varicella vaccination in Japan since 2014 has reduced varicella cases, however, breakthrough varicella still occurs. This study aimed to clarify the current distribution of VZV clade among pediatric varicella patients and adults with VZV‐associated central nervous system (CNS) infections in Japan. Skin swabs were collected from varicella patients (< 15 years) in Aichi Prefecture (September 2015–August 2017). Cerebrospinal fluid (CSF) samples were obtained from adult patients (> 15 years) with VZV‐associated CNS infections (November 2014–June 2023). VZV DNA was detected by PCR, and its clade was determined by sequencing open reading frame (ORF) 22 and ORF37 regions. Wild‐type and Oka vaccine strains were distinguished by loop‐mediated isothermal amplification (LAMP) method. Of 124 pediatric swab samples and 62 adult CSF samples 94.4% belonged to clade 2 and 4.8% clade 1. No clade 1 samples were detected in CSF samples. No vaccine strain was detected. Clinical characteristics did not differ significantly among clades. Clade 2 VZV predominates in both pediatric varicella and adult VZV‐related CNS infections in Japan with sporadic clade 1 varicella cases.