01.15.2021 07:00 AM

Everything We Know Now About Schools, Kids, and Covid-19

Researchers are finally getting good data on how severely SARS-CoV-2 affects children and how they transmit it. What does it mean for reopening classrooms?

student at desk — Photograph: ROBYN BECK/Getty Images

In the seemingly endless, heartbreaking history of the coronavirus pandemic, this past week has been the bleakest yet. Since last Thursday, Covid-19 has killed over 23,000 people in the US—the deadliest week in American history. Logistical snags are dragging down the vaccine rollout, and a dangerous new virus strain has begun to spread in at least a dozen states.

Everything You Need to Know About the Coronavirus

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By Eve Sneider

At a time when kids would normally be starting their spring semester, this post-holiday surge has many state and local officials again grappling with the polarizing issue of in-person education. In hard-hit Southern California, health authorities are calling for a total school shutdown across Los Angeles County. Meanwhile, in New York City, public officials are pushing to keep classrooms open, arguing that as cases in their city spike, schools might actually be the safest place for kids to be.

That we are still debating the extent to which schools drive the spread of SARS-CoV-2—or shield students from it—is largely the result of policies put forth by the outgoing Trump administration, which encouraged in-person instruction but discouraged data-gathering on Covid-19 in schools. At the national level, neither the US Centers for Disease Control and Prevention nor the Department of Education systematically track school outbreaks. That work has been left to willing academics and volunteers. But even the most comprehensive database, assembled by Brown University economist Emily Oster, still has gaps. That’s made it very difficult to decipher the relationship between schools, their mitigation strategies, and the virus’s spread in surrounding communities, even as thousands of natural experiments have unfolded around the country.

But there are other ways to learn things about how the coronavirus affects children.

Last January, as Covid-19 began to sweep across the globe, one of the surprising silver linings of the fast-moving public health crisis was that kids appeared to largely be left out of it. The earliest data from China and Europe showed that the coronavirus infected children only rarely, and mostly caused mild illness when it did. Over the last 12 months, observational analyses of tens of millions of Covid-19 cases and ginned-up surveillance studies have produced much better (though sometimes conflicting) data. Some of the initial science still stands. But much of it has evolved into a more nuanced understanding of how frequently young people pick up, spread, and suffer from SARS-CoV-2. And a year into this pandemic, scientists have finally accumulated enough evidence to say a few things for sure.

The first is that children are, as a whole, less susceptible to the worst outcomes of Covid-19 than people over the age of 18. “They get all the same illnesses as adults, just at a lower rate,” says Lindsay Thompson, a pediatrician and the vice chair for health outcomes and translational research at the University of Florida, who last month wrote a perspective in JAMA Pediatrics summarizing the lessons of the last year. How much lower? In the US, kids are between four and nine times less likely than adults to be hospitalized with Covid-19, and between nine and 16 times less likely to die, according to CDC data. “But it still happens,” says Thompson. “Children have died. Children are dying.”

It’s been happening more often in recent months, as the US’ fumbling, partisan pandemic response failed to arrest the virus’s spread and the rate of Covid-19 cases among children began to rise. Kids might be less likely to suffer the worst ravages of the disease. But when tens of millions of Americans are contracting Covid-19, even a low incidence of bad outcomes quickly starts to add up.

In April 2020, children under the age of 18 made up just 1.7 percent of reported coronavirus cases, according to data from the CDC. By August, that figure had shot up to 7.3 percent. As of January 13, 2021, more than 2 million kids have caught Covid-19, and children comprise 10.8 percent of the nation’s caseload. According to a report released by the CDC on Wednesday, about 12,000 kids were hospitalized with the disease between March 1 and December 12, 2020. During that time, 178 died.

Childhood, however, is not a monolith. Newborns and infants have consistently been found to be at the highest risk, along with kids with underlying health conditions. Then, as kids transform into teenagers, their bodies become more like adults and their social networks expand, putting them more at risk than elementary and middle school students. A pivotal shift appears to happen around the start of puberty. Researchers at the COVID Monitor, a group tracking data from more than 7,000 school districts in the US, recently found that infection rates among high schoolers are triple that of elementary-school-age children.

Age isn’t the only thing that matters. Black, Latino, and American Indian kids also suffer severe Covid-19 disease and death at higher rates than white children, in large part because of systemic racism that makes it harder for nonwhite Americans to access health care, housing, and the kinds of jobs that allow parents and older relatives to work from home. Black and Latino children have also disproportionately come down with a constellation of serious heart, gastrointestinal, and kidney complications following bouts with Covid-19. Known as multisystem inflammatory syndrome, or MIS-C, this still-mysterious ailment, while rare, has struck more than 1,600 kids by the CDC’s most recent count.

When it comes to the debate over opening schools, the other crucial questions are not about severity, but about spread. How easily are kids getting infected, and often are they transmitting the disease to others?

One way researchers have gauged that is to track infections within households where at least one person has tested positive. Two early studies in China found that kids were less likely than the adults in their household to contract the coronavirus. But scientists at the CDC had a hunch that something else was going on. The researchers leading those studies were only swabbing family members if they started to feel sick. Anyone who had been infected but wasn’t showing symptoms would be missed. Moreover, schools in the areas where the families lived were mostly closed. Kids were staying home, reducing their odds of exposure to the virus.

“Back then, there was a ton of discussion about how susceptible kids really were,” says Melissa Rolfes, a CDC epidemiologist with the agency’s Covid-19 response team. “So we set out to get really good data across age spans that wouldn’t be biased by things like symptoms or seeking medical care.”

Rolfes teamed up with researchers in Marshfield, Wisconsin, and Nashville, Tennessee, who’d worked with the CDC in the past on flu surveillance. They quickly stood up a new study focused on finding the coronavirus in kids. It worked like this: If a person tested positive for SARS-CoV-2 and they lived with at least one other person who wasn’t sick, the scientists would try to recruit that whole household for 14 days of daily nasal swabbing and questionnaire answering. That allowed them to capture any viral spread within the household, regardless of who showed symptoms.

What they found between last April and October was stark. People who had the virus spread it to half of their household companions. (In the earlier studies from China, it had been more like 20 to 30 percent.) And it didn’t matter whether it was a kid or an adult who brought SARS-CoV-2 home, they transmitted it to their family at similar rates. Within households, kids also got infected just as often as adults. But they tended to get less sick than the grown-ups, avoiding fevers and a cough most of the time. “Maybe they’d just have a stuffy nose, or maybe nothing, but when you swabbed them you’d find the virus,” says Rolfes. She realized earlier studies had been overlooking a lot of cases, especially in kids, because they didn’t appear ill. “We were really floored when we saw that data. A secondary infection rate above 50 percent for household contacts was just mind-boggling.”

The study is still ongoing, and Rolfes says those numbers haven’t changed much since October. The takeaway, then, is that symptomatic kids can spread the coronavirus just as easily as symptomatic adults. But Rolfe’s study was limited in one important way: It wasn’t designed to pick up instances when kids without symptoms bring the virus home—or how widely they spread it. To understand that phenomenon, she says, we’ll have to wait a little bit longer.

The CDC has several surveillance studies running in places like New York City, Baltimore, Seattle, Ann Arbor, and Puerto Rico, where researchers are following households for eight months, swabbing each home’s inhabitants every week, and testing them for SARS-CoV-2. That constant monitoring of healthy families should help illuminate how much people who don’t look or feel sick—especially kids—are driving coronavirus transmissions. It will also provide a clearer sense of how widespread asymptomatic infections are throughout the population. Rolfes says they expect that data soon.

Read all of our coronavirus coverage here.

Asymptomatic infections are really a good news/bad news story. According to a recent review of the best available evidence, people who show no symptoms seem to be about one-third as infectious compared to individuals who are sneezing, coughing, and generally just flinging contagious particles out of their lungs. That’s the good news. The bad news is people who don’t feel sick don’t tend to stay home. If they don’t—or they can’t—stay home, they’re bound to interact with others. And, as Johns Hopkins University epidemiologist Emily Gurley told WIRED a few months ago, “the more contacts everyone has, the more transmission there is.”

Currently, the CDC estimates that people who aren’t showing symptoms are responsible for nearly 60 percent of all SARS-CoV-2 infections in the US—though more than half of them will go on to develop symptoms later. New and better data from those studies could have an impact on what the CDC recommends in terms of continued mitigation strategies. “Right now, we’re relying a lot on modeling to understand the impacts of things like masks and social distancing and school closures,” says Rolfes. “As these studies start providing data, that’s really useful for refining these models.”

But those kinds of models can only go so far, says Muge Cevik, an infectious disease researcher at the University of Saint Andrews in Scotland, who is advising the British government on its Covid-19 response. “The main challenge with modeling is that school closures almost always coincide with additional mitigation measures in the community, like limiting people in bars and restaurants,” Cevik says. That means it’s nearly impossible to disentangle the influence of a school closure from the effects of other restrictions or voluntary changes in people’s behavior. Studies from the UK, Germany, Norway, and Ireland have shown some, though mostly minimal, spreading inside schools. But tracking how that contributes to overall transmission rates is a more daunting challenge. “We know that when we open schools we see more infections in kids. But do they spill over into the community?” she asks. “We still don’t have a clear answer to this.”

Still, there have been some super-spreading events at schools and other places where children congregate. The common threads uniting those incidents is that now-rote protective measures like social distancing, mask wearing, and improving ventilation weren’t rigorously enforced. And they happened in places where the virus was already circulating at very high rates.

We learned that from an outbreak at a Georgia YMCA camp, where kids didn’t have to wear masks inside their cabins or keep windows open at night while everyone slept. And from Israel, which opened schools without masking or social distancing rules, only to have thousands of students test positive for the virus weeks later. Similar stories played out in the US in places like Georgia, Nebraska, and Utah.

What scientists are starting to have a clearer picture of is how damaging the loss of in-person instruction has been to kids’ mental and physical well-being, as well as their education. Moving schools online severed millions of kids from regular meals they depend on. It upended systems designed to protect students from child abuse. And without the social fabric of schools, teens are experiencing anxiety and depression in shocking numbers. One troubling analysis performed by pediatricians and public health researchers at the University of Washington found that school closures in 2020 could be cutting the life expectancy of each child in primary school by an average of three months. And all of that is worse for Black, Latino, and American Indian kids, who disproportionately don’t have access to reliable internet connections and working computers.

So, to recap: Kids can catch the coronavirus, like anyone else, although nobody has managed to put a pin in exactly how susceptible they are compared to adults or to younger teenagers, who seem to occupy a middle ground. But they’re less likely to show symptoms, and way less likely to get seriously ill. If they don’t have symptoms, they’re (probably) not going to spread it to a bunch of other people. And kids under 10 are about half as likely to transmit the virus as adults. SARS-CoV-2 can and will spread through schools, but they seem to only become super-spreading hot spots when precautions like masks, distancing, and ventilation are ignored. Schools are always going to be a risk, but one that can be managed—and not being in school is also really bad for kids, for their parents, and for society as a whole. Which is perhaps why the CDC is now recommending that K-12 schools should be both “the last settings to close” and “the first to reopen,” when they can do so safely.

Does the arrival of new, more contagious virus strains change this calculus? Cevik cautiously says no—decisions should still be driven by the local prevalence of Covid-19 cases, and the same mitigation measures should be adequate, if strictly followed.

Initial analyses tracking the UK variant, known as B.1.1.7, through the British populace suggested that it was spreading faster among young people than adults. But Cevik says that was effectively a glitch in the data. The mutation emerged in November while the country was on lockdown but secondary schools were open. “It just had more of a chance to circulate among teenagers than anyone else,” she says. It’s still early, but all evidence so far suggests the UK variant increases transmission—by about 30 to 50 percent—equally across all age groups. So while schools might be a lot riskier, so is everywhere else people congregate indoors.

Because of that, the new variant has caused a frightening escalation of infections in the UK that are threatening to collapse the nation’s hospital systems. England’s prime minister, Boris Johnson, had pledged last year to keep schools open as long as possible. But kids went back to primary school for exactly one day in January before his government reversed course and closed them again amid the latest surge.

For places where the variant has not yet taken over, preemptively closing schools out of fear isn’t the answer, says Cevik, especially if there aren’t ways to financially help parents and other caregivers shelter at home. “Sometimes school closures are seen as an exit strategy for controlling infections, because it’s easier to close schools than to provide isolation support or housing to low-paid employees,” says Cevik. “But that won’t be an effective solution if we’re not doing enough to address the structural factors that are actually driving the pandemic.”

For Americans, that might change starting next week. President-elect Joe Biden has pledged to reopen most schools within his first 100 days in office. On Thursday, he unveiled his sprawling coronavirus plan, in which he proposed pumping out $1 trillion in direct aid to Americans for help with rent, food, child care, and utilities, in addition to funds for expanded testing and a speedier vaccine rollout. It's a sign that the US government is willing to start doing the structural work that will get kids back into classrooms.