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

Assessing vaccine effectiveness of publicly funded vaccination programs in Queensland

“…This finding is consistent with national ecological findings (58). The median age of people hospitalised with varicella did increase, however, reassuringly there was no increase in the incidence of varicella hospitalisations in those aged >40 years.…”

“…As the majority of HZ occurs in people aged ≥50 years, with incidence and severity increasing with age (240), the predicted increases in HZ could led to substantial increases in the burden of disease and healthcare costs. In order to prevent HZ among those at high risk, the Australian Government has recently announced public funding for a live-attenuated zoster vaccine Reassuringly, an analysis of national data from Australia found age-standardised hospitalisations rates for HZ were lower in the first 4.5 years of the VV program compared to the 1.5 years immediately preceding vaccine licensure (58). Another recent study comparing age-specific Australian HZ hospitalisation rates up to 6.5 years post VV public funding found rates remained stable in all age-groups, except aged ≥80 years, in whom there had been a significant increase compared to the pre-vaccine funded period (242).…”

“…year olds with no history of prior varicella infection or immunisation (221). Globally, single dose and, to a greater degree, two-dose childhood VV programs have been effective in reducing the burden of chickenpox (58,230,231). However, it has been hypothesised that high VV coverage, achieved through vaccination programs, may result in an increase in the incidence of herpes zoster (HZ) due to a reduction in exogenous boosting among people with a history of chickenpox (72).…”

“…Also funded through the NIP until 2016/2017 was an adolescent catch-up dose for children aged 10-13 years without a history of infection or vaccination (58). Prior to inclusion in the NIP, the only estimate of VE for VV in Australia came from a chickenpox outbreak at a child care centre in Western Australia in 2002 (59).…”

“…One study examining the incidence of herpes zoster in people over 65 years of age from 1992 to 2010 in the US found that age-specific incidence was increasing before introduction of the childhood VV program, and that the rate of herpes zoster increase did not significantly change following VV introduction (76). In Australia, herpes zoster hospitalisation rates were not found to have increased in any age-group when assessed up to June 2010 (58).…”