The UK government introduced a blanket 14-day self-isolation commitment on all incoming travellers on 8 June. This has been widely criticized for being too indiscriminate and too late. Should the UK have introduced restrictions early on in the outbreak rather than as it declines? 

Most countries have instituted restrictions of varying severity on incoming and outgoing travellers since the covid-19 pandemic took off, although the World Health Organization (WHO) has consistently advised against such measures. The UK government has until now been an outlier in imposing hardly any restrictions on entry while advising its own citizens not to travel abroad. 

It has now implemented its new policy. This has encountered vociferous opposition from the aviation, travel, and hospitality sectors as well as many Conservative politicians. The airlines threaten legal action against the government, calling the measures “illogical and irrational”, when the UK currently has significantly higher infection rates than almost all of its European neighbours. The scientific justification for a blanket self-isolation requirement is absent. On 3 June the Chief Scientific Adviser publicly distanced himself from the policy, saying it would make sense to target only those countries with higher infection rates. 

Many now ask why measures were not introduced months ago to prevent, or limit, imported cases from other countries. 

In theory, draconian travel or quarantine restrictions applied universally as soon as possible could help to prevent, or at least slow, the transmission of a virus from another country. The best example of early action to suppress an epidemic is New Zealand, which had its first recorded case as late as 28 February. On 15 March, when it had six recorded cases, it asked all visitors to self-isolate for 14 days. Four days later it closed its borders almost completely and then imposed a very rigorous lockdown. On 8 June New Zealand’s prime minister was able to lift all internal restrictions in the absence of any cases at all, while maintaining a rigorously closed border. 

Implementing similar measures in the islands of the UK, with their openness to international travel and tourism, is far more problematic. One problem is that when the need for possible action becomes apparent it may already be too late. It is more than likely that by the time the outbreak was notified to the WHO by China on 31 December 2019 the virus had already spread internationally. Anecdotal reports suggest UK infections in December and a patient in France was retrospectively found to have tested positive on 27 December. Recent research indicates the disease could have emerged in Wuhan as early as October 2019. Wuhan has a major airport serving other Chinese, regional and international destinations in Europe and the USA. A significant number of infected persons were likely to have reached a wide range of international destinations directly from Wuhan, or indirectly from other Chinese hubs or other destinations, before and after Wuhan and its airport were locked down on 23 January.      

In the case of the UK, there were 17.6 million arrivals by air between 1 January and 23 March when the lockdown was imposed. The Chief Scientific Adviser told MPs on 5 May that genomic data now indicated “a very large number of cases” coming from multiple European sources from late February. To have had a significant impact, an extensive ban or quarantine obligation, including for returning UK citizens, would have been necessary as early as possible.  

Yet the UK assessment of risk was “very low” initially and only raised to “moderate” on 30 January when WHO declared COVID-19 a public health emergency. It was finally raised to “high” on 12 March. 

Part of the reason for the lack of urgency shown by the government in this and other respects was the absence of good data on the actual number of infections. By 1 March 36 cases had tested positive in the UK. Retrospective analyses based on the actual subsequent trajectory of critical illness and mortality suggest there must have been many thousands of infections—one study estimates 12,700 cases by 1 March in England alone, rising to 1.85 million by 23 March when the UK finally locked down. Daily infections were then increasing by over 350,000. The simple fact is that the absence of adequate testing capacity disguised the severity and rapidity of the pandemic’s evolution, providing a false sense of security.  

Commenting on the desirability of an earlier lockdown in the UK, a government scientific adviser said recently, it was “hard to pull the trigger” in early March because the data were “really quite poor”. Similar considerations applied to the possibility of the imposition of travel restrictions, especially in the absence of data on the scale of likely imports from elsewhere. In both cases, the very high associated economic and political costs were deemed infeasible to guard against a risk which the government judged, wrongly with hindsight, to be low or moderate. 

Charles Clift is a senior consulting Fellow at the Centre on Global Health Security at Chatham House. He works as an independent consultant in the field of global health, including for the WHO, and is the author of publications on the role of the WHO in the international system.

Competing interests: None declared.