Recurrent vaccine-strain varicella zoster virus reactivation in a child with acute lymphatic leukemia.

This case illustrates recurrent herpes zoster (HZ) in a child with acute lymphatic leukemia. Interestingly, vaccine-strain HZ was confirmed by identifying the live-attenuated Oka vaccine strain (vOka) using metagenomic sequencing and sequence comparison at three loci that distinguish vOka from wild-type varicella zoster virus (VZV). Although vaccine-strain HZ is generally milder than HZ caused by wild-type VZV, prompt recognition and initiation of antiviral treatment is essential in immunocompromised patients, as fatal varicella due to disseminated vaccine-strain VZV has been reported in this high risk group.