Impact of varicella vaccination on the epidemiology of herpes zoster and postherpetic neuralgia: a narrative review.

Varicella-zoster virus (VZV) establishes lifelong latency following primary infection and can reactivate later in life to cause herpes zoster (HZ) and its debilitating complication postherpetic neuralgia (PHN). The implementation of varicella vaccinations has profoundly altered the epidemiological landscape of VZV. This narrative review examines the current literature to evaluate the impact of these vaccination programs on the incidence of HZ and PHN. Early mathematical models based on the "exogenous boosting" hypothesis predicted a substantial surge in adult HZ due to reduced exposure to circulating wild-type virus. However, long-term epidemiological data demonstrate that the incidence of adult HZ was already increasing prior to the introduction of vaccination programs and did not accelerate post-implementation, suggesting other primary drivers, such as an aging population. This review highlights the significant decline in HZ incidence among vaccinated pediatric populations, as the attenuated vOka vaccine strain is substantially less prone to reactivation than the wild-type virus. Furthermore, HZ that does occur in vaccinated individuals tends to be milder, resulting in a reduced risk of progression to PHN. To address the persistent risk in older adults, a recombinant zoster vaccine is recommended as a highly effective secondary prevention strategy. Despite challenges, such as breakthrough infections and the need for long-term monitoring of vaccine-induced immunity, varicella vaccination remains a cornerstone of public health, offering broad protection across different ages. Further research is needed to fully understand the long-term impact of varicella vaccinations on the incidence of HZ and PHN and to identify additional risk factors for these conditions.