There is something challenging to communicate in coronavirus reporting: Nearly 41,000 people have died from Covid-19 in the United States (and many more will die), and those deaths have come despite the unprecedented social distancing measures being taken across the country. Without them, the loss of life would surely be higher.
Unless or until scientists have data to back it up, though, the impact of social distancing is as much hypothesis and intuition as scientific fact. Luckily, a new study out of Hong Kong indicates that the precautious taken there — similar to those taken in the US, like closed schools, travel restrictions, mask-wearing, and general distancing — have had a measurable effect on the spread of Covid-19 and the flu. That should give people confidence that social distancing is working, even with its painful economic toll.
But as Americans consider when and how to begin relaxing those measures, they will have to balance health concerns with economic ones. That’s where another new study, this one from economists at the University of Chicago and Penn State, comes in handy. It reaches a useful conclusion: The best way to ease these lockdowns and alleviate the economic losses without inviting an untenable spike in cases and fatalities is to do it gradually — over a matter of months.
Taken together, these new studies offer a picture of America’s socially distant future: Even as people try to resume something resembling normal life, it will take time — and precautionary measures will have to be maintained.
Social distancing has demonstrably impeded Covid-19’s spread in Hong Kong
Hong Kong has taken many of the same steps the United States has to stave off the Covid-19 threat. It started closing schools and restricting travel from the Chinese hot spots in January. It has added new migration rules as well as mandatory quarantines for overseas travelers in the last few months and set up protocols for civil servants to work from home.
In addition, the public has responded by changing their behavior. According to this new study, led by researchers from the WHO Collaborating Centre for Infectious Disease Epidemiology and Control in Hong Kong, most people say they are avoiding crowded places (85 percent in March) and staying home as much as possible (75 percent). People are practicing better hygiene, too: The percentage who said they wear masks jumped from 75 percent in January to 99 percent in March, and the percentage who say they wash their hands more than usual leaped from 71 percent to 95 percent.
And as a result, local transmission in Hong Kong appears to be quite low. The metric used to measure transmission — which estimates how many people someone carrying the virus will infect — has hovered around 1. The goal is to push the threshold below 1, which if sustained will lead to the outbreak being contained. But even holding at around 1 is a success, compared to what we’d expect in nature (the virus has an estimated R0 of 2 to 2.25, though it’s still not clear exactly how contagious it is.)
The main reason Hong Kong saw a spike in Covid-19 cases in mid-March was because there was a sudden surge in cases imported from other countries (and Hong Kong started testing asymptomatic inbound travelers and requiring quarantines in response). This chart shows that locally sourced cases remain quite low and steady, allowing for the increase you would expect after people brought the virus onto the island from elsewhere.
But what’s great about this study is the authors don’t just rely on Covid-19 cases. They also tracked influenza infections over the same period and they found a notable downturn compared to prior years when schools were closed but no other social distancing measures were taken. Flu transmission dropped by 44 percent in February 2020 versus the 10-15-percent drops seen in 2009 and 2017-2018 during previous flu pandemics.
Our study suggests that measures taken to control the spread of COVID-19 have been effective and have also had a substantial impact on influenza transmission in Hong Kong. Although the transmission dynamics and modes of transmission of COVID-19 have not been precisely elucidated, they are likely to share at least some characteristics with influenza virus transmission, because both viruses are directly transmissible respiratory pathogens with similar viral shedding dynamics.23 The measures implemented in Hong Kong are less drastic than those used to contain transmission in mainland China, and are probably more feasible in many other locations worldwide. If these measures and population responses can be sustained, avoiding fatigue among the general population, they could meaningfully mitigate the impact of a local epidemic of COVID-19.
So social distancing — as defined by general crowd avoidance and some closures, paired with sanitary precautions — certainly appears to work, if this Hong Kong data is to be believed. The next question then is: How do countries start reopening?
A gradual reopening is the best way to balance economic and health concerns
Luckily, as the public conversation about easing social distancing picks up, economists from the University of Chicago and Penn State have come out with a statistical model that tries to find an ideal balance between relaxing lockdowns to reduce the economic toll of the pandemic while also attempting to minimize the loss of life.
It’s both a simple model (as the authors acknowledge) and also a highly technical paper, so read at your own interest. They assume there is no cure available but widespread testing is. Their conclusion is pretty straightforward: “[T]he optimal policy prescribes a lockdown starting two weeks after the outbreak, covering 60% of the population after 1 month. The lockdown is kept tight for about a full month, and is subsequently gradually withdrawn, covering 20% of the population 3 months after the initial outbreak.”
That’s easy enough to comprehend: To balance output and health risks, you start with a general lockdown and then gradually lighten up over a matter of months, with the most vulnerable people likely remaining in near-isolation for the longest period.
But it was another passage in the paper that left the biggest impression on me. The length of the lockdown, and the rate at which you relax it, depends highly on the statistical value you assign to a human life. The authors are clear that they ascribed a lower value because the people most vulnerable to dying from Covid-19 are older and have underlying health conditions. To be rigorous about these estimates, that makes some sense.
But if you start assigning more value to those lives, then the length of the lockdown that would be desirable grows substantially:
The value of the statistical life we use in our benchmark case (20 times annual GDP per capita) is on the low range of the estimates in the literature. Following Hall, Jones, and Klenow (2020), our benchmark value takes into account that the majority of the victims of the virus have a below average life expectancy. A higher value of statistical life (say 30 times annual GDP per capita), makes the abandonment of the lockdown more gradual, taking a bit more than six months to be totally abandoned. Considering a much larger value, in the order of 80 to 140 times the annual GDP per capita, implies a very strict lockdown that lasts for about 9 months, and a year after still has about 15% of the population in lockdown.
This is the calculation society will be asked to make over the next year or more. How do we balance the need to relax social distancing in order to begin climbing out of an unprecedented economic crisis that has affected millions, with the inevitable surge in Covid-19 cases, and deaths, that we would expect to result?
The takeaway of these two papers is clear: We must maintain certain safeguards (especially hygiene and limiting crowds), and when we start to relax some of these restrictions, we must do it gradually. We must also be nimble: Hong Kong initially sent civil servants back to work but then reverted to work-from-home protocols after its March spike. Restaurants didn’t face restrictions on their capacity in late March, when other social establishments were ordered closed for the first time.
As some people have put it, the end of social distancing will not be a switch (on, then off) but a dial (more, then less, then maybe more). As Donald McNeil Jr. wrote for the New York Times, after talking to more than 20 public health experts:
It was impossible to avoid gloomy forecasts for the next year. The scenario that Mr. Trump has been unrolling at his daily press briefings — that the lockdowns will end soon, that a protective pill is almost at hand, that football stadiums and restaurants will soon be full — is a fantasy, most experts said.
“We face a doleful future,” said Dr. Harvey V. Fineberg, a former president of the National Academy of Medicine.
Right now, the public is still on the side of preserving social distancing, despite the economic costs. But we must remind ourselves, and continue to remind ourselves, that we are in this for the long haul.
This story appears in VoxCare, a newsletter from Vox on the latest twists and turns in America’s health care debate. Sign up to get VoxCare in your inbox along with more health care stats and news.
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