Australian vaccine preventable disease epidemiological review series: varicella-zoster virus infections, 1998-2015

In 2005, the National Immunisation Program implemented a varicella vaccine for children aged 18 months, and in 2016, a herpes zoster (HZ) vaccine for adults aged 70-79 years. This epidemiological review analyses national trends in varicella and HZ for the years 1998-2015 to examine the impact of a funded varicella vaccine and provide a baseline for monitoring the impact of a funded HZ vaccine.

Varicella and HZ notifications (2002-2015), hospitalisations (1999-2013) and deaths (1998-2013) were sourced. We stratified analyses by age, sex and Indigenous status, and estimated rates and incidence rate ratios.

Funded varicella vaccine led to a rapid decline in varicella notifications, hospitalisations and deaths. During the post-varicella vaccine period, hospitalisations declined in all age groups <40 years, with greatest reduction of 84% in children aged 18-59 months. Annual HZ hospitalisation rate was 10.8 per 100,000. HZ hospitalisation rates increased with age and were highest in persons aged =75 years (87.6 per 100,000). Post-herpetic neuralgia (PHN) was diagnosed in 32.5% HZ hospitalisations with highest hospitalisation rate in persons aged =75 years (32.1 per 100,000). Varicella and HZ hospitalisation rates were significantly higher among Indigenous Australians. Twenty one deaths were coded as due to varicella and 340 deaths were coded as due to HZ in persons aged <40 years and =40 years, respectively.

The national varicella immunisation program substantially reduced varicella associated morbidity and mortality. Burden of HZ and PHN in Australia is substantial. Following the introduction of a funded HZ vaccine, timely and high quality surveillance will be crucial to assess the impact of the national HZ immunisation program.