This report outlines different models of COVID-19 infection and vaccination used to define a target level of vaccine coverage for transition to Phase B of the National plan to transition to Australia’s national COVID-19 response.

The model was based on the simplifying assumption of a single national epidemic, with COVID-19 transmission, severity and vaccine effectiveness as for the Delta variant.

Stated objectives of the immunisation program enabling the transition to Phase B are to constrain severe outcomes within clinical capacity and reduce the intensity and length of requirement for socially and economically impactful public health and social measures. o For ‘baseline’ levels of social and behavioural restrictions, rapid epidemic growth is expected at 50 and 60% coverage, with more substantial transmission reduction by 70 and 80% targets.