Reviewed by: Dr. Michael Payne, MD; London Health Sciences Centre
Exogenous boosting of immunity, through exposure to varicella-zoster virus (VZV) cases, is theorized to prevent herpes zoster (HZ) reactivation events in adults. The loss of these protective exposures was felt to potentially increase rates of HZ, post introduction of VZV vaccination programs, due to subsequent decreases in VZV circulation. This study utilized repurposed data from placebo recipients in a large multinational zoster vaccine clinical trial (ZOE-50). Countries were clustered based on their varicella vaccination program characteristics, as having high, moderate, or low VZV circulation. Anti-VZV antibody mean concentrations, median frequencies of VZV-specific CD4 T cells, and percentages of individuals with increases in VZV-specific CD4 T-cell frequencies were compared across countries and clusters. VZV-specific humoral immunity from 17 countries (12 high, 2 moderate, 3 low circulation) varied significantly between countries, but not by VZV circulation. No significant differences were identified in VZV-specific CMI between participants from low versus high circulation countries. Results show no consistent evidence of decreased VZV exposures in countries with universal VZV vaccination programs. This may explain why countries that have introduced varicella vaccination programs have not experienced theorized increases in herpes zoster incidence and this can inform decisions on implementation of national universal varicella vaccination programs.
References:
Stephane Carryn, et al. The Journal of Infectious Diseases, Volume 225, Issue 3, 1 February 2022, Pages 413–421, https://doi.org/10.1093/infdis/jiab500. Anne A Gershon, Michael D Gershon The Journal of Infectious Diseases, Volume 225, Issue 3, 1 February 2022, Pages 361–363, https://doi.org/10.1093/infdis/jiab501.