  Novel coronavirus disease (COVID-19) has spread across the world at an
unprecedented pace, reaching over 200 countries and territories in less than
three months. In response, many governments denied entry to travellers arriving
from various countries affected by the virus. While several industries continue
to experience economic losses due to the imposed interventions, it is unclear
whether the different travel restrictions were successful in reducing COVID-19
importations. Here we develop a comprehensive framework to model daily COVID-19
importations, considering different travel bans. We quantify the temporal
effects of the restrictions and elucidate the relationship between incidence
rates in other countries, travel flows and the expected number of importations
into the country under investigation. As a cases study, we evaluate the travel
bans enforced by the Australian government. We find that international travel
bans in Australia lowered COVID-19 importations by 87.68% (83.39 - 91.35)
between January and June 2020. The presented framework can further be used to
gain insights into how many importations to expect should borders re-open.
Authorities may consider the presented information when planning a phased
re-opening of international borders.
