A new study suggests that recurrent shingles is caused by the same herpes zoster (HZ) virus responsible for the first infection. The report in the journal Vaccine notes that HZ is caused by reactivation of varicella zoster virus (VZV) that established latency in sensory and autonomic neurons during primary infection.  

Researchers from the Department of Veterans Affairs San Diego Healthcare System and the CDC point out that in the Shingles Prevention Study, a large efficacy trial of live attenuated Oka/Merck zoster vaccine (ZVL), polymerase chain reaction–confirmed second episodes of HZ occurred in two of 660 placebo and one of 321 ZVL recipients. Those cases appeared in patients with documented HZ during a mean follow-up of 3.13 years.

The study team notes that an additional two ZVL recipients experienced a second episode of HZ in the Long-Term Persistence Substudy, adding that all episodes of HZ were caused by wild-type VZV.

“The first and second episodes of HZ occurred in different dermatomes in each of these five participants, with contralateral recurrences in two,” the authors explain.

The first and second episodes occurred from 12 to 28 months apart, according to the article, and one of the five participants, who was immunocompetent on study enrollment, was immunocompromised at the onset of his first and second episodes of HZ.

The researchers used VZV DNA isolated from rash lesions from the first and second episodes of HZ to sequence the full-length VZV genomes. “For the unique-sequence regions of the VZV genome, we employed target enrichment of VZV DNA, followed by deep sequencing. For the reiteration regions, we used PCR amplification and Sanger sequencing,” the authors write.

Results indicate that the VZV genomes from the first and second episodes of HZ in each of the five participants were caused by the same VZV strain. The authors add, “This is consistent with the extraordinary stability of VZV during the replication phase of varicella and the subsequent establishment of latency in sensory ganglia throughout the body. Our observations also indicate that VZV is stable during the persistence of latency and the subsequent reactivation and replication that results in HZ.”

Researchers note that studies of HZ recurrence have reported recurrence rates ranging from 0.5% during 10 years of follow-up to 6.4% during 6.5 years of follow-up, although rates were significantly lower in the studies they cited compared with those based on retrospective review of medical records.

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