Effectiveness of Voluntary PCR Testing Against COVID-19 Spread in Japanese Remote Islands

Abstract

Introduction: The global spread of coronavirus disease (COVID-19) has highlighted the challenges faced by remote and isolated regions, emphasizing the need for targeted preventive measures. However, the application of voluntary polymerase chain reaction (PCR) testing for travelers to remote Japanese islands has not been adequately assessed. We assessed whether voluntary PCR testing of travelers is effective for preventing the introduction of individuals with COVID-19 to remote islands in Japan. Methods: The implementation of PCR testing and its results over a two-year period were assessed. Through a simulation analysis, we also suggested the risk of infection spread when tests were not conducted. Results: Between September 2020 and September 2022, 38,943 of 45,900 travelers to the Ogasawara Islands underwent pre-travel PCR testing, with a significant increase in test uptake during emergency declarations. Ogasawara reported 385 positive COVID-19 cases, with no hospitalizations or severe cases among residents, contrasting with Tokyo's higher infection and hospitalization rates. The Wave 7 scenario analysis suggested that without pre-travel testing, the median number of infected persons could have reached 416, exceeding the actual number of 316, indicating that testing plays a role in protecting the community. Discussion: Our study demonstrates that voluntary pre-boarding PCR testing among travelers to remote Japanese islands effectively prevented COVID-19 introduction and transmission, with a high testing rate of 86.7%. Simulations indicate that without testing, infections could have been significantly higher. Acceptance was enhanced by government-covered costs and easy saliva sampling. Limitations include the voluntary nature (14% did not test) and potential false negatives from self-collected samples. Despite longer stays, infection rates remained low, highlighting the effectiveness of preventive measures and the adaptability of local healthcare systems. Future efforts should consider mandatory testing and more detailed data collection. Conclusion: Our findings confirm that pre-boarding PCR tests effectively prevented the spread of COVID-19 from urban to remote islands, reducing infections. It highlights the importance of combining pre-travel PCR testing with quarantine measures for arriving travelers. Thus, implementing pre-travel PCR testing is crucial for safeguarding remote islands against COVID-19. Our findings can facilitate the formulation of appropriate infectious disease control policies.