By James Paton
April 4, 2020
With confirmed cases of Covid-19 globally exceeding 1 million and more countries going into lockdown to slow the pandemic, the emerging question is: “When will this all end?” The answer depends in large part on uncertainties about the novel coronavirus that causes the disease, including whether you can get it more than once and how quickly the world’s scientists might produce a vaccine. The cost and benefits of a prolonged shutdown and what different countries can afford, from both an economic and political standpoint, are factors, too.
1. So how does this end?
There’s a consensus that the pandemic will only end with the establishment of so-called herd immunity. That occurs when enough people in a community are protected from a pathogen that it can’t take hold and dies out. There are two paths to that outcome.
- One is immunization. Researchers would have to develop a vaccine that proves safe and effective against the coronavirus, and health authorities would have to get it to a sufficient number of people.
- The second path to herd immunity is grimmer: It can also come about after a large portion of a community has been infected with a pathogen and develops resistance to it that way.
2. How do we manage until then?
For many countries, the strategy is to lock down movement to dramatically slow the spread, closing businesses and schools, banning gatherings and keeping people at home. The idea is to prevent a huge burst of infections that overwhelms the medical system, causing excessive deaths as care is rationed. “Flattening the curve” staggers cases over a longer period of time and buys authorities and health-care providers time to mobilize --
- to build capacity for testing,
- for tracking down contacts of those who are infected, and
- for treating the sick, by expanding hospital facilities, including ventilators and intensive-care units.
3. When can restrictions loosen?
The public shouldn’t expect life to return to normal quickly. Lifting restrictions too early risks inviting a new spike. Authorities in China began to re-open the city of Wuhan, where the pandemic began, two months after it was sealed off from the world, when transmission had virtually halted. But China’s measures were stricter than anywhere else so far, and at least one county has gone back to a lockdown. England’s deputy chief medical officer, Jenny Harries, said lockdown measures there need to last two, three or, ideally, up to six months. Annelies Wilder-Smith, a professor of emerging infectious diseases at the London School of Hygiene and Tropical Medicine, recommends restrictions stay in place until daily cases drop consistently over at least two weeks.
4. Then what?
A road map authored by a group of U.S. health specialists including former Food and Drug Administration commissioner Scott Gottlieb calls for an intermediate stage in which schools and businesses would reopen but gatherings would still be limited. People would continue to be encouraged to keep at a distance from one another, and those at high risk would be advised to limit their time in public. If cases begin to rise again, restrictions would be tightened. Their report, published by the pro-business American Enterprise Institute, is arguably more optimistic than the future envisioned by researchers at Imperial College London. Their models suggest that for at least two-thirds of the time until herd immunity is established, all households would need to reduce contact with schools, workplaces or the public by 75%. In any case, the widespread availability of testing is important in this stage. At the heart of the U.S. plan: at least 750,000 tests per week.
5. Why is testing so important?
This virus is wreaking so much havoc, not because it’s especially lethal, but because it’s insidious; many who are infected are well enough to go about their daily business, unwittingly spreading it to others. That makes it vital to test for infection widely in the population, and to test everyone with symptoms. That way, those who are infectious can be put in isolation and everyone they’ve had close contact with while contagious can be tracked down, tested and if necessary isolated as well, limiting the spread in the community. Another kind of test looks for antibodies to see who has already beaten the virus and is thus unlikely to be re-infected, at least for a time. Once widely available, such tests might enable people who test positive for antibodies to move about more freely.
6. Why does where you are matter?
Authoritarian countries such as China can impose stricter controls on movement and more intrusive means of surveillance, such as house-to-house fever checks, tracing and enforcement of quarantines, and are less vulnerable to pressure from businesses and popular opinion. That gives them powerful tools to keep the virus in check, so long as they are vigilant against imported cases. That’s a more difficult proposition for other nations. The poorest countries can less easily afford the economic losses caused by prolonged restrictions, and often don’t have the health infrastructure for extensive surveillance.
7. How long will a vaccine take?
Dozens of companies and universities around the world are working on it, but there’s no guarantee they will prevail. Vaccine development normally is a long and complex process that includes years of testing to ensure shots are safe and effective. In the coronavirus fight, some of the players aim to deliver a vaccine in 12 to 18 months, an extraordinarily ambitious goal. As well as using tried-and-true approaches, scientists are relying on new technologies, like those that add viral genetic material to human cells, inducing them to make proteins that spur an immune response. Some vaccine specialists believe governments, citizens and investors should temper their optimism. It’s not clear if the methods will work, that the timelines will be met or that companies will be able to manufacture enough shots.
8. What about the second path to herd immunity?
First, it would occur only if recovering from an infection leaves people with lasting immunity. It’s not yet known if that’s the case with the novel coronavirus. The portion of a population that would have to be exposed to the virus to establish herd immunity is also unknown. Generally, it’s high, for example 75% for diphtheria and 91% for measles. Patrick Vallance, the U.K. government’s chief scientific adviser, estimated the figure at 60% in February. How long it would take to reach the necessary threshold would depend on measures governments impose in response to the pandemic. Without tight restrictions, it would be faster yet come at a steep cost in illness and deaths as health systems would be overburdened. Some research assumes the actual number of infections is much higher than the confirmed cases. If that’s true, countries are closer to herd immunity than we know.
9. Are there other variables?
We could get lucky, and the virus could fade with the onset of summer in the northern hemisphere, where most cases are, just like outbreaks of influenza subside with seasonal changes. But it remains unknown whether warmer weather will play a role. Even if the outbreak wanes, it could return in the fall. Some are pinning their hopes on an ultra-effective therapy or a cure.
The Reference Shelf
Related QuickTakes on what you need to know about Covid-19, how it transmits, the quest for treatments and a vaccine, and the seasonality question.
Bloomberg News looks at the hurdles to development of a coronavirus vaccine.
The roadmap published by the American Enterprise Institute and the modeling done by Imperial College London.
An article in MIT Technology Review argues that the pandemic will change our lives, in some ways forever.
A commentary in the New York Times suggests the near future will be like a roller coaster ride.