Scientists are often quick to remind the public: no model is perfect.
After Professor Neil Ferguson’s computer model suggested in March that 500,000 people in the UK would die of the coronavirus without lockdown measures, the UK quickly abandoned its herd immunity strategy and resorted to shutting down schools and businesses.
A June review in the journal Nature showed that some researchers were able to reproduce Ferguson’s findings, but software engineers said the code was messy and some public-health experts said the results were unreliable.
One finding in particular didn’t seem to make sense: The model showed that closing UK schools and universities during a lockdown actually led to more COVID-19 deaths than if schools had stayed open.
A new peer-reviewed report published in the BMJ on Wednesday suggests that takeaway could be accurate.
“Our first thought was that it was a mistake, but after a little work on the code, we replicated the result,” Graeme Ackland, the study’s author, wrote. “The basic explanation for this counter-intuitive result is that an intervention that substantially suppresses the first wave of the epidemic leads to a stronger second wave once the interventions are lifted.”
Other experts still aren’t convinced.
“This result applies to a specific, and probably unrealistic, scenario and should not be interpreted as a prediction,” Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, said in a statement.
The model assumes that people behave a certain way during lockdown: namely, that suspected cases isolate at home, households voluntarily quarantine, and people over 70 years of age distance themselves from others. That latter measure has proven difficult to enforce, experts say.
“Many of the most vulnerable require the care of other members of the population,” Matt Keeling, a professor of populations and disease at the University of Warwick, said in a statement. “While it is easy to switch off this component in a model, achieving this is practice is far more difficult.”
Under all of the model’s scenarios, lockdown measures are completely lifted after three months. The model also assumes that lockdowns will be lifted before an effective vaccine becomes available.
“This gives rise to a strange set of scenarios where a second wave is allowed to progress in an uncontrolled manner,” Keeling said.
Indeed, Ackland acknowledged that “the result only holds if there’s no successful vaccination program for a couple of years.”
Infections could peak after schools reopen
There’s an inherent logic to shutting down schools during the pandemic: Fewer interactions mean fewer opportunities for the virus to transmit from one person to the next.
A July study found that closing US schools in the spring may have been associated with 1.37 million fewer cases over a 26-day period and 40,600 fewer deaths over a 16-day period. Surveys conducted in Wuhan and Shanghai also found that closing schools reduced peak infections in those cities by up to 60%.
The UK model doesn’t deny that school closures can lower transmission. But it suggests that reopening schools could have their own dire consequence: Cases may spike again dramatically, leading to a higher demand for ICU beds compared to the first wave of infections. When ICUs become overcrowded, it increases the risk that infected people will die.
The US has already seen cases rise in response to colleges reopening: A September study that’s still awaiting peer review found that reopening colleges for in-person classes added more than 3,000 new coronavirus cases per day to the US tally since July.
But local outbreaks depend on how much the virus is spreading when a school reopens. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has suggested tailoring school reopenings to the level of transmission in each community for this reason.
Many schools have also implemented strict mask policies — a measure that could prevent cases from spiking above pre-lockdown levels. Germany, for instance, reopened schools in August without any major outbreaks. Many students there are required to wear masks in hallways and on school buses.
Israel, meanwhile, saw infections surge after school reopened, but teachers there reported that masks and social distancing weren’t strictly enforced.
“Israel [closed schools] and they did see more disease, but they also had a lot of community-based transmission happening at the same time,” Yvonne Maldonado, an epidemiology professor at Stanford University, told Business Insider. “Other countries didn’t shut down and didn’t have that issue, but they also were very careful.”
The cost of keeping schools open
The UK model assumes that some school-aged children would have developed immunity to the virus had schools remained open. Since this group is less vulnerable to severe infection, the scenario may have resulted in fewer deaths compared to school shutdowns.
“If you lock down everybody, the virus is spread amongst everybody, whereas if you leave the virus to spread amongst those who aren’t actually going to die, then by the end of the pandemic, the deaths are more concentrated in the older group,” Ackland told the BBC’s “Today” radio show on Thursday.
But there are obvious consequences to that strategy. Young people can still get very sick or develop long-term symptoms that persist for several months or more. Those who get infected can also transmit the virus to more vulnerable people.
“Since this virus transmits as easily as it does, targeting one age population would not have had much of an effect,” Dr. Rachel Graham, an assistant epidemiology professor at The University of North Carolina at Chapel Hill, told Business Insider. “If you let all of your school-aged children wander free and transmit to and from each other, they still have to go home to parents and grandparents.”
Nevertheless, the model emphasizes that lockdowns are a short-term solution to the pandemic. In the long-run, Graham said, there are only two possible outcomes: vaccination or herd immunity.
“A vaccine will definitely shorten the amount of time that measures have to be as strict,” she said. “The only other option is to establish a significant herd immunity. And the only way you can do that is if you infect more people. That’s a significant human cost that I don’t think anybody’s really willing to take at this point.”