Assessing the Mass Vaccination Campaigns in Australia and Their Impact Over the Delta and Omicron Outbreaks

Background: The Australian Government implemented a national vaccination campaign against SARS-CoV-2 on February 22, 2021, but the roll out was initially slow and widely criticised. After January 2022, the large-scale Omicron outbreak resulted in a massive number of cases and deaths, although mortality rates would have been far higher if not for invigorated efforts to rapidly mass vaccinate the entire population. This is the first assessment of the population impact of the vaccination campaign.Methods: Limited publicly accessible data restricted the study to the State of NSW, which serves as a reasonable guide for Australia. Weekly death rates were derived among 50+ individuals with respect to vaccine status between August 8, 2021, and July 9, 2022. Through modelling, we evaluated the impact of the vaccination campaign on the number of deaths across a range of counterfactual scenarios.Findings: Amongst 50+ individuals, the unvaccinated had a 7.7 (/11.19) times higher risk of death than those with 2nd dose (/booster). Had NSW fully vaccinated its ~2.89 million 50+ residents earlier, or initiated its booster campaign earlier, this would not have prevented a substantial number of the 3,495 total observed 50+ deaths. The booster campaign prevented an additional 2,200 (63%) of total 50+ deaths by July 9, 2022. Reducing the increasing rate of coverage per dose to 85% (similar to the US), resulted in an additional 640--1,560 deaths. In the absence of a vaccination campaign, an estimated 21,250 COVID-19 50+ deaths, i.e., ~6 times the total observed, could have been expected in NSW.Interpretation: The Australian vaccination campaign was found successful in significantly reducing death rates over 2022, relative to other countries and to alternative hypothetical vaccination scenarios. The success was due to policy makers ability to react in real time to changes and invasion of new SARS-COV-2 variants, and in rapidly achieving high levels of vaccination coverage (full and booster) in short time periods, and in a timely fashion that reduced waning.Funding: This project was supported by RMIT University.Declaration of Interest: All authors declare no competing interests.