Herpes zoster in Australia: evidence of increase in incidence in adults attributable to varicella immunization?

Abstract

Rates of herpes zoster (HZ) hospitalizations, antiviral prescriptions, and New South Wales emergency-department presentations for age groups <20, 20-39, 40-59 and ⩾60 years were investigated. Trends were analysed using Poisson regression to determine if rates increased following funding of varicella immunization in Australia in November 2005. The regression analysis revealed significantly increasing trends of between 2% and 6% per year in both antiviral prescriptions and emergency-department presentations in all except the <20 years age group. When considered together, the differential changes in rates observed by age group provides preliminary evidence to indicate that HZ incidence is increasing in adults aged >20 years. However, it is not possible to attribute the increasing trends in HZ observed directly to the varicella immunization programme, and continued monitoring and analyses of data for a longer duration, both pre- and post-vaccine introduction, is required.

Varicella and herpes zoster hospitalizations before and after implementation of one-dose varicella vaccination in Australia: an ecological study

“…[30][31][32] Some epidemiological studies have reported temporal increases in the crude HZ hospitalization rates. 19,33 However, only two other studies have assessed trends in age-standardized HZ rates before and after vaccine introduction, including hospitalizations and health care utilization, and showed no temporal increase in HZ (Table 5). 35,36 Increasing age is the greatest risk factor for VZV reactivation, due to agerelated decline in cellular immunity, high prevalence of chronic disease and use of immune-compromising medication.…”

Trends in Nationwide Herpes Zoster Emergency Department Utilization From 2006 to 2013

“…Other studies have found an increasing incidence of HZ in the United States and other countries, consistent with our findings. 2,[18][19][20][21] The cause for this elevation in disease burden is unclear and is likely multifactorial. The age-specific increased rate of HZ-related ED visits in patients aged 20 to 59 years may be explained in part by the Hope-Simpson hypothesis that increased varicella zoster virus vaccination has led to a rise in overall HZ incidence.…”

Decreased varicella and increased herpes zoster incidence at a sentinel medical deputising service in a setting of increasing varicella vaccine coverage in Victoria, Australia, 1998 to 2012

“…Although the deputising service data reported here indicate variability in zoster consultations, we have described a clear increasing trend in presentations for zoster in community patients younger than 70 years, and found some indication of a decreased number of consultations for zoster in the community among those aged 80 years and older. A mixed picture of age-related changes in zoster has been reported from various data sources in various countries [18,19,27,28]. However, compared with many other countries, Australia has relatively high childhood varicella vaccine coverage, which may impact on zoster, as well as varicella, incidence.…”