Objective:

To retrospectively evaluate COVID-19 travel restrictions enforced in Japan from 2020 through 2022 and analyze their impact on imported infections. To retrospectively evaluate the impact of reduced international travel volume during COVID-19 travel restrictions in Japan from 2020 through 2022 on imported SARS-CoV-2 infections. To retrospectively evaluate the impact of reduced international travel volume during COVID-19 travel restrictions in Japan from 2020 through 2022 on imported SARS-CoV-2 infections.

Approach:

• Epidemiological Data: The study analyzed weekly airport screening tests and positive results from October 2020 through October 2022 and monthly border-entry data from 2017 through 2019.
• Epidemiological Model: Investigators used a quasi-experimental approach to estimate infection risk among travelers and model counterfactual travel volumes based on prepandemic border-entry patterns. The analysis estimated differences in imported infections between observed and counterfactual travel-volume scenarios.

Key Findings:

• Japan began implementing COVID-19 travel restrictions in February 2020, with restrictions expanding as the pandemic progressed.
• From January 9, 2021, through May 31, 2022, all travelers entering Japan were screened and tested for SARS-CoV-2.
• From October 2020 through May 2022, approximately 1.0 million border entries were observed compared with an estimated 49.5 million under the 3-year mean counterfactual scenario, representing an approximately 98% reduction.
• Assuming infection risk among travelers was the same under observed and counterfactual scenarios, reduced travel volume was associated with an estimated 530,000 to 620,000 fewer imported infections.
• The largest estimated reduction in imported infections was associated with travelers from the Western Pacific Region.

Interpretation:

The findings suggest that the substantial reduction in international travel volume during the pandemic was associated with a similarly large reduction in estimated imported SARS-CoV-2 infections. However, the estimates reflect reductions in travel volume overall and cannot be attributed entirely to specific travel-restriction policies. The findings suggest that the substantial reduction in international travel volume during the pandemic was associated with a similarly large reduction in estimated imported SARS-CoV-2 infections. However, the estimates reflect reductions in travel volume overall and cannot be attributed entirely to specific travel-restriction policies.

Limitations:

• The main analysis was limited to October 2020 through May 2022 because published entry-screening results were available for that period.
• Counterfactual travel volumes were based on prepandemic data, although the pandemic itself may have reduced travel even without formal restrictions.
• The analysis did not account for specific events that may have affected travel volume, such as the Tokyo Olympic Games.
• The model assumed that observed airport-screening positivity represented infection risk among travelers under the counterfactual scenario, although traveler characteristics may have differed without restrictions.

Conclusion:

From October 2020 through May 2022, Japan experienced approximately 48.5 million fewer border entries than estimated under the 3-year mean counterfactual scenario. Under the study’s assumptions, the reduced travel volume was associated with an estimated 530,000 to 620,000 fewer imported SARS-CoV-2 infections. From October 2020 through May 2022, Japan experienced approximately 48.5 million fewer border entries than estimated under the 3-year mean counterfactual scenario. Under the study’s assumptions, the reduced travel volume was associated with an estimated 530,000 to 620,000 fewer imported SARS-CoV-2 infections.