Herpes zoster is a sporadic disease occurring as a reactivation of the VZV in individuals who have previously had chickenpox. Approximately one in three people will develop zoster during their lifetime with the incidence rising as cell-mediated immunity to VZV declines with age.3 The annual risk for adults aged over 60 years is 1.1 per 100 persons.2
Recurrence is greater in females than males (about 7 percent after eight years compared with 4 percent for males). Third episodes are rare.
VZV is present in lesions of herpes zoster and is transmissible via contact with the vesicles to other susceptible individuals (causing chickenpox). Airborne transmission can occur from immune-compromised individuals with disseminated HZ. Episodes of HZ in older individuals provide a constant mechanism for reintroducing the virus, causing varicella in non-immune individuals who are in close contact, who then spread the virus to other susceptible individuals.
Several countries have published mathematical models of the potential impact of the VZV childhood vaccination programme on the incidence of HZ. These models predict a possible increase in HZ over the next few decades following the institution of a childhood programme, followed by a rapid decline, based on the absence of circulating VZV to boost immunity. However, it is still not known whether circulating VZV does contribute to reducing varicella zoster disease, and therefore whether the introduction of childhood mass VZV vaccination does significantly alter the epidemiology of HZ. Studies that have investigated this issue have been unable to attribute any increase in incidence of HZ to the childhood VZV vaccine programme.4–8 (See also section 21.3.1).
Zoster hospitalisations by age group during 2013 are shown in Figure 22.1 below, with more than 60 percent occurring in adults aged 60 years and older. Hospitalisations are predicted to account for only a very small proportion of the overall HZ cases as most are managed in primary care.
Source: Ministry of Health