No one yet knows whether the Omicron variant of COVID-19 will be devastating or no big deal. On the “no big deal” side, there’s not currently evidence that it makes people sicker than previous strains, so it’s possible that it will simply wash over a global population rich in COVID antibodies. On the “potentially devastating” side, the Omicron variant seems to feature an especially large number of mutations, including some that scientists worry make it more likely than earlier strains to evade the COVID-19 vaccine. The Biden Administration’s line so far has been that Omicron is a “cause for concern, not a cause for panic.” Its first policy intervention, developed last weekend, while the President was on Nantucket for Thanksgiving, was to ban travel from eight countries in southern Africa, where the strain was first identified. On Tuesday evening, the Centers for Disease Control and Prevention announced new testing requirements for inbound international travellers. “Here’s what it does: it gives us time,” Biden said, in a speech explaining the policy. Among its overseas allies, the United States was on common ground. The United Kingdom adopted a similar policy. Japan, which has been more restrictive since the start of the pandemic, simply banned all international arrivals, sealing itself off.
These responses were immediately controversial, in part because South Africa— which maintains a robust genomic-surveillance program, and speedily reported the new variant—seemed to be getting punished for good global citizenship. Days before Biden’s travel ban went into effect, the strain was detected in the U.K., Germany, and the Czech Republic, but none of the European countries were singled out. “What you worry about is whether a country will be as forthcoming next time, if the result is they get a travel ban imposed on them,” Nicole Errett, a resilience researcher at the University of Washington, said. But the measures were also immediately controversial because public-health travel bans nearly always are: they engage central political tensions between contagion control and individual freedom, and between the health of one country and the well-being of the world.
The history of such bans runs deep, back to the quarantine controls developed by Italian cities during the plagues of the fourteenth century, when ships suspected of carrying the contagion were required to raise a quarantine flag upon entering harbor, and port cities were closed to ships arriving from plague-infested areas. (The quarantine flag lasted as a tradition; eventually, it was standardized to be yellow.) The bans took on a more modern shape at the end of the nineteenth century, when rudimentary tests began to allow public-health authorities to screen new arrivals. “By the eighteen-nineties, when there was a cholera epidemic in New York harbor, they could do stool samples and do a bacterial culture right away, and figure out if they’re infected or not,” Howard Markel, a physician and medical historian at the University of Michigan, said. Travel bans went into a senescence after the First World War, first because of a lack of international coöperation between the wars and then because of the seeming triumph of antibiotics. They reappeared once globalization helped revive pandemics, beginning in the eighties. Some of the travel bans, such as one on H.I.V.-positive travellers, in place from 1987 to 2010, were a bad match for the ways in which the disease was spread, though others, such as a temporary restriction on travel from Asia during the SARS crisis, seemed to help. Markel drew a comparison between the U.S., which had only eight laboratory-confirmed cases of SARS and no deaths, and Canada, which had no travel restrictions, and where an outbreak centered in Toronto’s hospitals killed forty-four people and put the city into quarantine.
In general, Markel said, when testing was available it allowed public-health authorities to follow the medical imperative “Don’t use a bazooka when a BB gun will do.” But, in the first phase of the coronavirus pandemic, many countries opted for the bazooka. Taiwan, South Korea, Japan, Singapore, Australia, and New Zealand all imposed severe travel restrictions, in many cases pairing them with aggressive contact tracing and testing regimes. The economic, social, and political costs of these policies could be extreme: Australia closed its borders to all non-residents, and some Australians living abroad faced fines or prison time if they tried to return home. New Zealand shut out even those foreign nationals married to New Zealand citizens. As a public-health measure, though, these restrictions appear to have been effective. In Taiwan, fewer than nine hundred people have died of COVID-19. Japan’s population is thirty-seven per cent that of the United States, yet it has had 2.3 per cent of the deaths. Australia, a vast country of twenty-six million people, has had just over two thousand deaths from COVID. In New Zealand, just forty-four people have died.
This week, as many countries began to impose new travel rules in response to Omicron, Tedros Adhanom Ghebreyesus, the director-general of the World Health Organization, asked them to refrain from the most restrictive versions. “Blanket travel bans will not prevent the international spread of Omicron, and they place a heavy burden on lives and livelihoods,” he said on Wednesday. But that is at least somewhat contradicted by the experience of the Pacific Rim countries during the pandemic. Peter Baldwin, a historian at U.C.L.A. who last year published a book on the first wave of global response to the pandemic, said, of the W.H.O.’s position, “I just do not get this logic because the travel bans, it seems to me, have proven that they’re quite effective.” Of course, no travel ban, Baldwin added, was airtight. “It doesn’t hermetically seal a country off—some virus will sneak in for sure—but they still managed to get a grip on the problem in a way that the countries that don’t do it, don’t.” The choice about whether to institute travel bans would be easy if they did not ever work—the humanitarian position of maintaining open borders would also be the prudent one. But in this pandemic, that hasn’t seemed exactly the case. Baldwin said, “It’s a political decision on W.H.O.’s part to not advocate travel restrictions, and you can see that because most countries totally ignore it.”
One reason that countries imposed severe restrictions at the outset of the pandemic was the difficulty of identifying who might be contagious. Unlike with Ebola, which is not thought to be transmissible unless a person is experiencing a fever, and for which a temperature check is therefore an effective screening tool, many travellers carried COVID-19 out of China without being detectably sick at all. As much as the Trump Administration bragged about its ban on travel from China, it was both too late and too porous to be truly effective. The U.S. imposed the ban only after forty-five other countries had already done so, after COVID-19 cases had been documented within the U.S. It also did so selectively, so that Americans and their dependents could travel unimpeded. Céline Gounder, an infectious-disease specialist and epidemiologist at N.Y.U. and Bellevue Hospital and a member of the Biden COVID-transition advisory board, told me, “In that situation you really need to close travel to everyone, regardless of the country that they’re travelling from, or their citizenship, or residential status. And you need to really do it fast. And that might have had an impact, especially for a place like New York City. That kind of time matters.”
Studies of the first phases of the pandemic have shown exactly how much it matters. Fifteen years ago, Alessandro Vespignani, a physicist at Northeastern, developed a model that simulates all human movement around the globe in order to predict, as minutely as possible, how diseases might spread. “Essentially, we built a synthetic world,” Vespignani told me. In a paper published in Science in April of 2020, Vespignani and his collaborators showed that worldwide bans on travel from Wuhan were initially quite effective—in early February, they estimated, the restrictions reduced the number of coronavirus cases around the world by seventy-seven per cent. Ultimately, Vespignani’s team found that the travel bans only had only a “modest effect” on the spread of the disease, postponing it by two to three weeks. But they did buy health authorities around the world some of the time that the Biden Administration now says it needs.
I called Vespignani because I wanted to know what he and his model made of the Omicron variant. “It’s like ‘Groundhog Day,’ ” Vespignani said to me—the news took him back to the spring of 2020. About an hour before we spoke, the C.D.C. had announced the first confirmed American case of the Omicron variant, in California. His model suggested that, given the known prevalence of the disease in other countries, there were likely “tens to hundreds” of Omicron carriers in the United States. “It’s not just one,” he said. Vespignani noted that, of the six hundred passengers on two recent flights from South Africa to Amsterdam, five per cent had tested positive for Omicron. If the many other flights leaving South Africa during the second half of November had similar numbers, that meant the virus would be well established all over the world.