Data published in Vaccine demonstrated that varicella zoster virus (VZV) is extremely stable during the varicella replication phase and subsequent establishment of latency in sensory ganglia throughout the body. Results of the study also showed the stability of VZV during latency, reactivation, and later replication that results in herpes zoster.
Investigators assessed the clinical characteristics of the first and second episodes of herpes zoster in 5 participants of the Shingles Prevention Study (SPS) and a Long-Term Persistence Sub-study (LTPS). Sequencing data of the complete genome sequences of the 10 viruses causing these herpes zoster cases were also presented and each pair of viruses from the first and second episodes were compared to see whether they were distinct or identical.
During the SPS, a large efficacy trial of live attenuated Oka/Merck zoster vaccine, second episodes of herpes zoster were confirmed via polymerase chain reactions in 2 of 660 placebo and 1 of 321 vaccine recipients with documented herpes zoster cases over a mean follow-up period of 3.13 years. A further 2 vaccine recipients experienced a second episode during the LTPS.
All herpes zoster episodes were caused by wild-type VZV; the first and second episodes occurred in different dermatomes in each of the 5 patients. Two patients had contralateral reoccurrences. The time between episodes ranged from 12 to 28 months and 1 of the participants who was immunocompromised at study enrollment demonstrated an immunocompromised state at the onset of both the first and second herpes zoster episodes.
Sequencing of the VZV DNA isolated from dermatologic lesions during the first and second episodes revealed that in all 5 participants both episodes were caused by the same VZV strain. According to investigators, 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.”
Investigators noted that the study was limited because both the STPS and LTPS were only carried out at 12 of the 22 SPS study sites, and enrollment was not randomized or blinded to study drug assignment. In addition, during the SPS the placebo population shrank as placebo recipients received the vaccine; therefore, there were no SPS placebo group members in the LTPS. This meant that because of differences in these study populations, data could not be combined to calculate an overall rate of herpes zoster recurrences throughout the SPS and its persistence substudies.
Investigators concluded that “VZV is extremely stable during the replication phase of varicella and the subsequent establishment of latency in sensory ganglia. VZV is also stable during latency, reactivation, and the subsequent replication that results in [herpes zoster].” Furthermore, they believe that it is reasonable to anticipate that in most patients who are immunocompromised, first and second herpes zoster episodes will be caused by the same strain.
Harbecke R, Jensen NJ, Depledge DP, et al. Recurrent herpes zoster in the Shingles Prevention Study: Are second episodes caused by the same varicella-zoster virus strain? [published online October 31, 2019]. Vaccine. doi:10.1016/j.vaccine.2019.10.038