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.”