Guidance

COVID-19 risk assessment methodology for inbound international travel

Published 24 November 2020

This guidance was withdrawn on 10 May 2021

This has been replaced by COVID-19 risk assessment methodology to inform international travel traffic light system.

A publication from the Joint Biosecurity Centre

Introduction

International travel corridors have been created to allow people to travel to the UK from specified countries, territories or islands without having to self-isolate on arrival. However, those entering the UK must ensure they comply with any wider national COVID-19 interventions or restrictions in place.

Ministerial decisions on international travel corridors are informed by risk assessments provided by the Joint Biosecurity Centre (JBC), working closely with Public Health England (PHE), using a methodology endorsed by the 4 Chief Medical Officers (CMO) of the UK.

Methodology

Risk assessments focus on the public health risk, posed by incoming travellers, to the UK population. The JBC and PHE monitor information from over 250 countries, territories and islands daily to inform these risk assessments.

Weekly incidence rate per 100,000 population, test positivity, imported cases and rates of change are key indicators used to identify specific countries, territories or islands that may be considered for an increase or decrease in risk rating. These countries, territories or islands are subject to deep dives.

Deep dives bring together a broader number of quantitative and qualitative indicators in order to make a more complete assessment of the risk posed, taking into account data limitations and biases. Deep dive indicators include:

• an estimate of the proportion of the population that is currently infected (this is known as ‘point prevalence’)
• weekly incidence rate and population size of the country, territory or island (noting smaller population sizes will show more volatility)
• trends in incidence, deaths, hospitalisations and intensive care admissions
• information on laboratory capacity, testing and contact tracing strategies, and test positivity rates
• COVID-19 cases detected in the UK with recent international travel history (imported infections)
• qualitative information related to the reliability of reported data and the maturity of public health systems
• public health measures in place and the enforcement of, and adherence to, those measures
• variations of the above metrics within countries, territories or islands, and information on disease clusters

Risk assessments take a relative and dynamic approach: countries, territories or islands with a similar or better COVID-19 risk position than the UK, based on the above indicators, are considered for travel corridors. The rationale for this is that the impact of travel restrictions is expected to be greatest when UK infection rates are relatively low. As UK infection rates rise, the relative risk to UK public health from imported cases decreases.

These relative assessments account for geographical variation in indicators across the UK. This is because, while the impact of imported infections to areas with very high case rates could be small, the same would not be true for areas of the UK with lower case rates. The JBC’s risk assessments therefore compare indicators in overseas countries or territories to the corresponding indicators for the bottom third (the lower tertile) of UK nations or regions when ranked.

A country or territory will be considered for a reduction in risk rating once its key indicators, taking into account both the level and growth rate of the indicators, have sustainably fallen below those for the bottom third (the lower tertile) of UK nations or regions (usually for at least 14 days – one COVID-19 incubation period).

Countries or territories can also be rated as a high risk to UK public health from inbound travel when their indicators are below those for the UK, but they exceed a maximum absolute threshold. This maximum absolute threshold identifies countries or territories as very high risk irrelevant of the UK situation, where the health system of a country or territory could be overwhelmed and where there would be significant transmission risk on return journeys to the UK. Its calibration also takes into account the UK domestic context.

The JBC takes a sub-national approach only when there is a clear boundary or border to a region, access to reliable and accurate health data for that specific region and travel routes to the UK without travelling through the non-exempt countries or regions. To date, this approach has only been established for islands.

The methodology for assessing risk to inform international travel corridors will evolve to reflect the changing pattern of the COVID-19 epidemic and as the JBC incorporates new scientific insights, new data sources, and new analyses that become available. It is subject to quarterly review (as a minimum) by the JBC Technical Board, chaired on a rotating basis by the 4 UK CMOs.