How will mass-vaccination change COVID-19 lockdown requirements in Australia?

TL;DR

This study uses an agent-based model to evaluate how Australia's hybrid COVID-19 vaccination strategy could reduce epidemic growth and lockdown measures, emphasizing the importance of mass vaccination in controlling future outbreaks.

Contribution

It introduces a large-scale agent-based model tailored to Australia's demographic and epidemiological data to assess the impact of mixed vaccine efficacy strategies on COVID-19 control.

Findings

Vaccination can reduce lockdown needs by up to 43%.

Epidemic growth rate can be decreased by 52%.

Peak daily cases can decrease by up to two orders of magnitude.

Abstract

Background: To prevent future outbreaks of COVID-19, Australia is pursuing a mass-vaccination approach in which a targeted group of the population comprising healthcare workers, aged-care residents and other individuals at increased risk of exposure will receive a highly effective priority vaccine. The rest of the population will instead have access to a less effective vaccine. Methods: We apply a large-scale agent-based model of COVID-19 in Australia to investigate the possible implications of this hybrid approach to mass-vaccination. The model is calibrated to recent epidemiological and demographic data available in Australia, and accounts for several components of vaccine efficacy. Findings: Within a feasible range of vaccine efficacy values, our model supports the assertion that complete herd immunity due to vaccination is not likely in the Australian context. For realistic scenarios in which herd immunity is not achieved, we simulate the effects of mass-vaccination on epidemic growth rate, and investigate the requirements of lockdown measures applied to curb subsequent outbreaks. In our simulations, Australia's vaccination strategy can feasibly reduce required lockdown intensity and initial epidemic growth rate by 43% and 52%, respectively. The severity of epidemics, as measured by the peak number of daily new cases, decreases by up to two orders of magnitude under plausible mass-vaccination and lockdown strategies. Interpretation: The study presents a strong argument for a large-scale vaccination campaign in Australia, which would substantially reduce both the intensity of future outbreaks and the stringency of non-pharmaceutical interventions required for their suppression.