Question Number: 225
PDR Number: SQ22-000595
Date Submitted: 21/11/2022
Department or Body: Department of Health

Question 117 The Therapeutic Goods Administration (TGA) may consider the background rate for a certain diagnosed clinical condition in Australia as part a vaccine safety signal investigation process. This is known as the Observed versus Expected (OvE) analysis. The TGA’s OvE analysis compares the observed rate of an adverse event reported for a particular vaccine, to the background rate that would occur in the population. Based on internationally accepted and standard processes and current evidence from published literature, the TGA’s OvE analysis uses a number of different data sets to derive background rates, depending on the adverse event. This can include rates taken from the published literature, health data provided by groups such as the National Centre for Immunisation Research and Surveillance and internationally accepted background rates that reflect similar populations to Australia. Careful consideration is required to determine the appropriate background rate to use. Generally, background rates from 2017-2019 are preferred for OvE analyses. Background rates from 2020 are considered less suitable because of the uncertain impact of the pandemic on general health data collection measures including healthcare utilisation.

Question 118 In 2020, before vaccines were available, the mortality from COVID-19 in Australia was 3.2%, and about 12.5% of infected people were hospitalised (available at: www.aihw.gov.au/reports/burden-of-disease/the-first-year-of-covid-19-inaustralia/summary). In 2022, there have been approximately reported 9.7 million COVID-19 cases in Australia, although projections from some serosurveillance surveys put this figure at over 15 million for 2021 and 2022. A mortality rate of 3.2% based on the lower figure of 9.7 million would equate to over 300,000 deaths and a hospitalisation rate of 12.5% would equate to well over a million in this period. However, since the vaccination roll-out the mortality rate in 2022 has reduced to 0.1%. Had the vaccine rollout been delayed by three years, it is not an unreasonable estimate that COVID-19 related hospitalisations in Australia could have reached several million. It is acknowledged that the Omicron variants have been of lesser severity, but they also arrived in a community with very high two-dose vaccination rates, which very significantly reduced hospitalisation and deaths. The impact of vaccination on COVID-19-related hospitalisations and deaths during the Omicron phase has been clearly demonstrated. Recent data from the US Centre for Disease Control identifies that hospitalisation and death is more than five-times higher in unvaccinated compared to vaccinated individuals. Furthermore, vaccination with an updated bivalent booster reduces the risk of death by 14.9-fold (available at: www.covid.cdc.gov/covid-data-tracker/#vaccine-effectivenessbreakthrough).