Background Decisions to impose temporary travel measures are less common as the global epidemiology of COVID-19 evolves. Risk-based travel measures may avoid the need for a complete travel ban, however evaluations of their effects are lacking. Here we investigated the public health effects of a temporary traffic light system introduced in the United Kingdom (UK) in 2021, imposing red-amber-green (RAG) status based on risk assessment.

Methods We analysed data on international flight passengers arriving into Scotland, COVID-19 testing surveillance, and SARS-CoV-2 whole genome sequences to quantify effects of the traffic light system on (i) international travel frequency, (ii) travel-related SARS-CoV-2 case importations, (iii) national SARS-CoV-2 case incidence, and (iv) importation of novel SARS-CoV-2 variants.

Results International flight passengers arriving into Scotland had increased by 754% during the traffic light period. Amber list countries were the most frequently visited and ranked highly for SARS-CoV-2 importations and contribution to national case incidence. Rates of international travel and associated SARS-CoV-2 cases varied significantly across age, health board, and deprivation groups. Multivariable logistic regression revealed SARS-CoV-2 cases detections were less likely among travellers than non-travellers, although increasing from green-to-amber and amber-to-red lists. When examined according to travel destination, SARS-CoV-2 importation risks did not strictly follow RAG designations, and red lists did not prevent establishment of novel SARS-CoV-2 variants.

Conclusions Our findings suggest that country-specific post-arrival screening undertaken in Scotland did not prohibit the public health impact of COVID-19 in Scotland. Travel rates likely contributed to patterns of high SARS-CoV-2 case importation and population impact.


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McLachlan, I., Huntley, S., Leslie, K., Bishop, J., Redman, C., Yebra, G., Shabaan, S., Christofidis, N., Lycett, S., Holden, M., Robertson, D., Smith-Palmer, A., Hughes, J. & Nickbakhsh, S. 2023, 'Evaluating public health effects of risk-based travel policy for the COVID-19 epidemic in Scotland'. To be published in medRxiv [Preprint]. Available at: https://doi.org/10.1101/2023.08.20.23293987

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Last updated: 03 May 2024
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