UK government significantly underestimating effectiveness of air passenger testing schemes
- Oxera, Edge Health and Dr Kit Yates have partnered to bring together their analytical, modelling, epidemiological, health sector and aviation expertise in order to review papers from Public Health England (PHE), the London School of Hygiene & Tropical Medicine (LSHTM) and the Animal and Plant Health Agency (APHA), which form the basis of the UK government’s current quarantine policy.
- The PHE paper, which underpins the government’s decision making, concludes that testing on arrival at an airport would identify only ‘7%’ of virus cases. However, this significantly underestimates the effectiveness of passenger testing.
- The PHE model assumes that all travellers who are infected and detectable with a test prior to departure do not board flights to the UK. Therefore, the 7% cited by the government only accounts for travellers who become detectable during the course of their flight. Instead, Edge Health and Oxera estimate that up to 63% of infected passengers attempting to enter the UK could be prevented from doing so with a testing scheme—vastly higher than the 7% figure offered by PHE.
- The PHE paper is based on a theoretical model and is not calibrated to real-world data. It does not consider actual infection rates in the country of origin and therefore fails to provide any real insight into the relative risk that inbound travellers pose to the UK population.
- This review by Oxera and Edge Health has been submitted as evidence to the UK government’s Global Travel Taskforce to support the development of a passenger testing regime policy to replace 14-day quarantine.
New independent analysis by Edge Health and Oxera has found ‘significant methodological concerns’ in work by PHE, which means the detection rates for passenger testing on arrival are being ‘significantly understated’.
Unlike 30+ countries, including Germany and Italy, the UK has not introduced any form of scheme to test travellers for COVID-19, instead implementing a 14-day quarantine policy and establishing ‘travel corridor’ countries and islands that are exempt (passengers do not have to isolate). This policy is driven in part by evidence from PHE that testing on arrival at an airport would identify only ‘7%’ of virus cases.
This new review, which has been authored by leading consultants and supported by academics including Dr Kit Yates, co-director of the Centre for Mathematical Biology at the University of Bath, finds that the PHE paper is based on a theoretical model that does not account for real-world data and therefore underestimates the rate of detection from airport testing on arrival. In reaching its 7% conclusion, PHE does not take account of potential travellers who are in theory detectable or symptomatic before the flight takes off. But these travellers would be detected by an on arrival testing scheme if they flew to the UK and therefore need to be accounted for in considering the effectiveness of a testing regime.
By contrast, although the review also identifies shortcomings with the LSHTM and APHA outputs, the LSHTM paper finds that an on arrival test would reduce the number of infectious travellers released into the community by about 45%, and the APHA paper quotes detection rates of 39.6% for a testing on arrival scheme. Edge Health and Oxera estimate that up to 63% of infected passengers attempting to enter the UK could be prevented from doing so with an on arrival testing scheme—vastly higher than the 7% figure offered by PHE.
Other key findings of the review include:
- Both PHE and LSHTM assume 100% compliance with quarantine, which is not supported by recent evidence, and therefore should be considered in determining how to open up safe travel to and from the UK. For example, according to evidence from SAGE, only around 20% of those reporting symptoms of COVID-19 in England report fully self-isolating.
- The effectiveness of testing regimes should take account of the demographics of infected people in a country of origin, and particularly the demographics of those people who are likely to fly. The PHE model does not do this.
- As all three papers are based on a simulation modelling technique known as Monte Carlo simulation, it is important to align the assumptions and the outputs with real-world evidence, which is currently lacking in the three papers’ approach. In addition, the assumptions in the three papers vary considerably and, in a number of cases, are not based on the most recent empirical evidence.
- The papers assume that the objective of the testing strategy would be to reduce the risk of ‘seeding’ community transmissions from flight passengers to zero. However, the government has established travel corridors based on an acceptable level of risk, rather than zero. These two positions are inconsistent.
Oxera and Edge Health share this analysis for consideration by the UK government’s Global Travel Taskforce, which is expected to report its findings to the Prime Minister in early November.
George Batchelor, Cofounder and Director of Edge Health, said:
‘The way in which the PHE model is set up means that only a tiny proportion of infected passengers—those who become symptomatic or are asymptomatic but detectable by a PCR test during the flight—can be detected at arrival. This means the widely quoted 7% excludes anyone who is in theory detectable or symptomatic before the flight takes off. This evidently isn’t the case, and it leads to an underestimation of the effectiveness of testing on arrival (the 7% figure), raising serious questions about its role in informing government policy on passenger testing.’
Michele Granatstein, Partner at Oxera and Head of the Aviation practice, said:
‘All three papers are based on theoretical simulation models. As with all models, the outputs are only as good as their inputs. Since there may be no consensus in the empirical evidence regarding certain input assumptions, it is therefore very important that outputs are calibrated with real-world evidence from established airport testing regimes.’
The authors of the report are:
Dr Kit Yates, Senior Lecturer and co-director of the Centre for Mathematical Biology in the Department of Mathematical Sciences, University of Bath
George Batchelor, a Cofounder and Director of Edge Health, a leading analytics firm that works with the NHS
Michele Granatstein, Partner at Oxera, leading its Aviation team and advising airports, airlines, regulators and policymakers across Europe and internationally
Dr Eva Deuchert, Senior Adviser at Oxera
Jennifer Connolly, an experienced health economist from Edge Health
Mona Sachter, an Analyst at Oxera
Maria Starovoitova, a data scientist from Edge Health
The independent review was commissioned by a consortium of airlines, airports and industry organisations: Virgin Atlantic, IAG, TUI, Heathrow, MAG, Collinson, Airlines UK and IATA.
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