The impact of earlier reopening to travel in the Western Pacific on SARS-CoV-2 transmission

Abstract

Background: The COVID-19 pandemic has led to a fall of over 70% in international travel, resulting in substantial economic damages. The impact is especially pronounced in the Asia-Pacific region, where governments have been slow to relax border restrictions.

Methods: A retrospective approach was used to construct notional epidemic trajectories for eight Asia-Pacific countries or regions, from June to November 2021, under hypothetical scenarios of earlier resumption of international travel and selective border reopening. The numbers of local infections and deaths over the prediction window were calculated accordingly.

Results: Had quarantine-free entry been permitted for all travellers from all the regions investigated, and travel volumes recovered to the 2019 levels, Australia, New Zealand, and Singapore would have been the three most severely affected regions, with at least doubled number of deaths, while infections would have increased marginally (< 5%) for Japan, Malaysia, and Thailand.

Conclusions: Earlier resumption of travel in Asia-Pacific, while maintaining a controlled degree of importation risk, could have been implemented through selective border-reopening strategies and on-arrival testing. Once countries had experienced large, localized COVID-19 outbreaks, earlier relaxation of border containment measures would not have resulted in a great increase in morbidity and mortality.

Keywords: Border measures; Quarantine; SARS-CoV-2; Testing; Travel restrictions.

Figure 1

Local cases averted by border containment measures in 2021. Comparisons between daily case counts with (‘observed’ — dots in blue for reported case counts) and without (‘notional’ — in red, with line for mean and shade for 95% CrI) implementation of travel restrictions (i.e. quarantine requirement for foreign visitors after their arrival) from June to November 2021, assuming the numbers of foreign visitors were the same as those in the real situation. For presentation purposes, observed incidence is presented for every third day.

Figure 2

Infection size comparisons for scenarios with diverse tourism recovery dates. Comparisons (mean and 95% CrI) of infection sizes (from the start of tourism resumption to the end of November) between scenarios with different tourism resumption dates, ranging from the first day of June to November. The reference scenario assumes numbers of foreign visitors remained the same as those in 2021 throughout the 6-month simulation window. In each scenario, no movement restriction was imposed on foreign visitors upon their arrival.

Figure 3

Infection size comparison for borders reopening to different regions. Times of total infections (mean and 95% CrI) for each region by the end of the 6-month simulation period (from June to November 2021), compared with the real situation, under selective opening of borders to some of the other regions (from one to seven, ordered by risk), assuming communication among the regions had recovered to pre-pandemic (2019) levels throughout this period.