At first glance, Covid-19 seemed to be a shared global experience, in terms of both the incidence of the disease and how countries responded. But now it has become clear that countries are diverging significantly in terms of strategy and outcomes. This means that, as the world exits from lockdowns, it will enter another difficult phase: Lock-ins that severely limit international travel.
Tourism, trade, and travel more broadly will never be the same again. The full pattern remains unclear, but lock-ins are likely to slow the global economic recovery – and to create another round of crisis, at least in small island economies that depend on short-stay international visitors.
Today, national Covid-19 strategies can be broadly separated into three categories: eradication, herd immunity, and suppression of the coronavirus until a vaccine or cure is discovered.
Eradication is the hardest to achieve. New Zealand claims to have gotten there; and Australia aspires to do the same. This approach is most likely to succeed in pristine and relatively remote areas, such as the northern Canadian territory of Nunavut, which currently has no reported cases.
By contrast, some countries will end up – for various reasons – with what epidemiologists call “herd immunity.” In these places, enough people will become infected and survive – and, it is hoped, acquire some degree of immunity – that the disease will no longer be able to spread like wildfire.
Sweden’s technocrats appear to have chosen to pursue herd immunity for their country. Japan’s official communications have been less clear, but the limited lockdown – and the failure of contact tracing in some contexts – suggests that herd immunity will occur. Brazil’s president calls this same approach “vertical isolation.” 
India, much of Africa, Asia, the Middle East, and Latin America seem to be on a similar path. 
If the basic reproduction rate (the now ubiquitous R0, which measures infectiousness) is 2.5, then 60% of the population in these countries likely need to get the disease before herd immunity is established. If R0 is higher, more people need to become infected and survive for herd immunity to occur. In any case, billions of new infections presumably still await.
The third category comprises countries that, while unable to eradicate the disease, are trying hard to suppress outbreaks for as long as possible. These countries, which include the United States, most of Canada, and Europe (other than Sweden), are in a tough spot. Although they have lowered the number of new cases with indiscriminate lockdowns, they have already shrunk economic activity by 10-25%, and now they enter a long slog to suppress R0.
South Korea and China demonstrate that, with social co-operation and authoritarian zeal, countries can rapidly identify the newly infected, trace all their contacts, and quarantine the exposed until the danger of disease is well past. These methods are being attempted but are much less likely to succeed comprehensively in the US and other developed countries, owing to varying access to healthcare, mixed confidence in the authorities, and wide income disparities. 
Some residents will be reluctant to report symptoms for fear of losing income, being taken away from their children, or having to pay high healthcare costs. Pockets of disease will rise and fall.
How does this affect global mobility and national economies?
Consider the mythical island of New Cookland. Having eradicated Covid-19, the island’s residents now – correctly – see “outsiders” as a potential Trojan Horse. Anyone arriving by plane will likely be welcomed by agents in hazmat suits, who will escort them to special quarantine zones, where all newcomers will be required to wait out the virus’s incubation period, and then be tested. A negative result is required to enter the country, and those who test positive will be quarantined for a further 15 days. Such restrictions and uncertainties will make travel to and from New Cookland quite unappealing.
In the real world, all countries striving to suppress R0 will impose similar restrictions on international arrivals. Their quarantine, self-isolation, and testing rules will be just as onerous as New Cookland’s.
By contrast, countries seeking to establish herd immunity won’t fear foreign visitors. The Swedes will be happy to invite us in, including for short stays. But if they invite themselves to other countries, that won’t please the eradicators and suppressors, who will fear “herd immunity” people. After all, herd immunity does not eradicate the disease, it just means there will be fewer cases of it, and little risk of an epidemic – but only in places where sufficient immunity has been established.
Gone are the days of short international travel, or long trips visiting multiple countries. We will all fear that a false positive test result will land us in an unnecessary quarantine for 15 days. Sterilisation of freight and other shipments will be similarly tough, especially for cargo coming into eradicators like New Cookland.
Tests establishing the presence of antibodies might ultimately lead to some relaxation of travel restrictions, depending on the extent of immunity that past infection is found to confer. But, in the absence of universal vaccination, tighter constraints on human mobility will presumably remain in place – perhaps for a long time. – Project Syndicate

* Peter Boone is Chairman of Effective Intervention at the London School of Economics’ Centre for Economic Performance. 
* Simon Johnson is a professor at MIT Sloan and co-chair (with Retsef Levi) of the Covid-19 Policy Alliance, focused on actionable intelligence and operational recommendations to limit the human damage from the pandemic.