Pre-departure PCR testing of travellers for SARS-CoV-2 was an effective tool in limiting transmission in Greenland during the early phases of the COVID-19 pandemic

Background: During the early part of the COVID-19 pandemic, travel restrictions were implemented in Greenland to contain SARS-CoV-2 transmission. Despite their widespread use, empirical evidence supporting the effectiveness of travel restrictions is scarce. Greenland was in a unique position to maintain pre-departure testing among travellers, and we aimed to describe the effectiveness of pre-departure testing to inform the implementation of travel restrictions in future outbreaks. Methods: Our analysis included SARS-Cov-2 PCR test results from travellers, including children, arriving in Greenland from Denmark between June 15, 2020, and January 26, 2022. Additionally, we identified positive tests performed within 14 days post-arrival to Greenland in this population. We estimated the sensitivity of pre-departure screening by dividing the number of positive cases identified pre-departure by the sum of cases identified pre-departure and within 14 days post-arrival in Greenland. Results: Our analysis covered around 43% of all travellers who underwent pre-departure screening. Out of 26,406 SARS-CoV-2 PCR tests, the proportion of positive tests was 0.6%, which varied over time according to the incidence in Denmark. Overall sensitivity of pre-departure screening was 59% and decreased over time, reaching a minimum of 36% in January 2022. The overall proportion of positive PCR post-arrival tests among all travellers was 0.4%. Conclusions: Implementing pre-departure PCR testing for SARS-CoV-2 among travellers can be effective in the early stages of outbreaks, particularly in geographical regions like Greenland where community transmission had not yet occurred. Our findings suggest that pre-departure screening of travellers contributed to delaying community transmission in Greenland compared to most other countries, thereby reducing the COVID-19 disease burden.