Before Jasmin got covid-19 last year, she was an especially active 10-year-old. She loved dancing, swimming, and gymnastics. “She was always upside-down, doing handstands,” says her mother, Binita Kane. Although she only had a mild case of the virus, she developed lasting, debilitating symptoms that kept her out of school. Jasmin, now 11, has abandoned her activities. Today, she uses a wheelchair.
Jasmin is one of an unknown number of children with long covid. She regularly suffers from fevers, a sore throat, weak and achy limbs, dizziness, and exhaustion, but the symptoms of long covid in children vary greatly. We don't know how many children are affected, and we don’t know which symptoms came from infections and which might have resulted indirectly from the pandemic. Scientists can’t even agree over what it means for children to have long covid.
Clinicians and epidemiologists find themselves at loggerheads over the issue—but this is more than just an academic spat. The lack of understanding means that potentially millions of sick children are not getting the treatments they need. “There’s been a real lack of support, understanding, research, and treatments for children,” says Kane, who is a consultant respiratory physician at Manchester University NHS Foundation Trust in the UK.
Sizing up the problem
The World Health Organization defines adult long covid as a condition that occurs usually three months after a confirmed or probable SARS-CoV-2 infection, with symptoms that last for at least two months that can’t be otherwise explained. Symptoms commonly include fatigue, brain fog, and shortness of breath.
The existence of a proper definition means that long covid can be diagnosed. The condition has been recognized as a potential disability under the Americans with Disabilities Act since July 2021, which should offer affected individuals protection from discrimination. So far, there is no agreed-upon definition for long covid in children.
One of the most heated arguments among doctors and scientists is over how significant a problem long covid in children really is. Estimates of the prevalence can swing between 1.8% and 67%, depending on the size of the study, which children are included, and how their symptoms are measured. As a result, some researchers warn parents to protect their children from a poorly understood syndrome that may affect them for the rest of their lives, while others say the risks have been overstated.
The debate hasn’t been helped by the lack of large and rigorous studies.
“Some papers are so bad,” says Sonia Villapol at Houston Methodist Research Institute in Texas, who, along with her colleagues, recently attempted to estimate the prevalence of long covid in children by analyzing all of the studies published so far.
Many children won’t have been tested for SARS-CoV-2, the virus behind covid-19, either because they are asymptomatic or because they have mild symptoms, she says. Some children might have been infected with SARS-CoV-2 without developing covid-19. Her team’s analysis suggests that around 25% of children who contract the virus will have at least one symptom four weeks after their infection.
Terence Stephenson of the UCL Great Ormond Street Institute of Child Health in London is involved in one of the more highly regarded research efforts into long covid in children. The team is tracking the outcomes of thousands of adolescents aged 11 to 17 in England who tested either positive or negative for SARS-CoV-2. The team’s latest published work found little difference in the prevalence of any lasting symptoms between children who tested positive versus children who tested negative: two-thirds for positive versus just over half for negative. Both groups experienced similar symptoms; headaches and tiredness were especially common.
What does this tell us? It depends on whom you ask. Study co-author Shamez Ladhani, pediatrician and epidemiologist at Public Health England, says the findings should reassure parents that long covid is very unlikely to affect their children.
Ladhani also points to data collected from smartphone app users. Health science company ZOE and King’s College London launched the COVID Symptom Study app in March 2020 and have since collected daily symptom reports from hundreds of thousands of contributors. Reports by parents on behalf of 1,734 children found that just 4% of infected children still had symptoms 28 days after the start of their illness.
The children tended to get better with time, says Emma Duncan, an endocrinologist at King’s College London who co-authored the ZOE study. Just under 2% of children still had symptoms 56 days after the start of their illness.
Once the children who had asymptomatic infections, who wouldn’t have taken a test at all, are factored in, the percentage of infected children who develop long covid is likely to be significantly lower than even 2%, says Duncan.
“Long pandemic syndrome”
One still-unanswered question is why so many children who tested negative for covid seem to experience lasting covid-like symptoms. Some of them might be related to other illnesses, but many could be a result of living through the pandemic, says Duncan.
Similar trends are emerging in data collected in the US. Chris Forrest is a pediatrician at the Children’s Hospital of Philadelphia and principal investigator at PEDSnet, a network of children’s health care services that is researching long covid in children. Forrest and his colleagues are about to publish research on the outcomes of around 660,000 children in the US who underwent PCR testing for SARS-CoV-2.
In unpublished work, they examined 500 different outcomes for kids who had contracted the virus versus those who didn’t. Common symptoms post-infection included changes to smell and taste, hair loss, and chest pain. Fatigue was almost as common in the kids who hadn’t had covid as those who had, Forrest says.
“The point is that the pandemic has been terrible for children,” says Duncan. “With school disruptions, family disruptions, educational disruptions … it’s been terrible for all children, irrespective of whether they personally contracted SARS-CoV-2 or got covid-19.” The phenomenon has been described as “long pandemic syndrome,” says Villapol.
Pediatricians describe a significant uptick in the numbers of children being referred to mental health care services. Doctors are seeing more children with eating disorders and tics, as well as an increase in symptoms of depression and anxiety. Very few studies have looked at the impact of social changes like school shutdowns, says Forrest.
Because many people experience headaches and tiredness—the most common symptoms identified in the ZOE study—on a regular basis, it’s hard to draw conclusions about long covid, says Deepti Gurdasani, a clinical epidemiologist and statistical geneticist at Queen Mary University of London. “Statistically, you will not find a signal, because the signal has been massively diluted,” Gurdasani says. Based on the data she’s seen, Gurdasani believes that long covid affects somewhere between 10% and 20% of children who contract the virus, which includes those who don’t develop covid-19 symptoms. Stephenson thinks the figure is around 7%.
"The point is that the pandemic has been terrible for children"Emma Duncan at King's College London
London-based pediatrician Michael Absoud says the figure can’t be as high as even 7%, because he just hasn’t seen enough children with suspected long covid. “We’ve set up post-covid clinics across London, which covers a big, big area,” he says. “We’ve seen 90 [children] since the beginning of July. That’s a small number.”
But many children might not make it to one of the specialized long covid clinics, says Sammie Mcfarland, founder of the campaign group and nonprofit Long Covid Kids. Both Mcfarland and her 16-year-old daughter have long covid, and they have been told that her daughter’s symptoms are “all in her head,” she says.
Having heard from other parents of children with long covid, Mcfarland says her daughter’s experience “is far from unique.” Primary care doctors don’t agree on what long covid in children is, and some don’t believe it is a syndrome at all. Others might send children for basic blood tests and scans that come back clear, and discharge them. “Everyone has a different opinion,” says Mcfarland.
A “squishy” syndrome
Part of what makes defining long covid difficult is that it appears to take many forms. An acute covid infection is rarely life-threatening to children, although a significant number of children have died—over 1,000 in the US alone. But a small number of children can develop a dangerous condition in which many of their organs become inflamed, known as multisystem inflammatory syndrome in children (MIS-C) or pediatric inflammatory multisystem syndrome (PIMS), which can result in lasting organ damage if left untreated. As of March 28, the CDC reported 7,880 cases of MIS-C in the US, which have so far resulted in 66 deaths. But there is disagreement over whether MIS-C falls under the umbrella of long covid or not.
Children develop many other difficult-to-define syndromes after having covid. Fatigue is common. Some children might have a cough or sore throat for months. Others take months to recover their sense of taste and smell. Some are too weak to attend school or have signs of heart damage, others experience seizures and blackouts. Symptoms can temporarily resolve before relapsing. Some children have a single lasting symptom, while many others experience a constellation.
The symptoms vary in their severity, too—and these differences may be overlooked in studies that compare children who did or did not contract SARS-CoV-2. A questionnaire that asks children if they had a headache might not differentiate mild head pain from a severe experience that leaves a child unable to open their eyes or get out of bed.
In truth, long covid is likely to encompass several different conditions. “It’s not a diagnosis, it’s not a disease … we don’t know what it is,” says Forrest. “It’s squishy.” Stephenson and Mcfarland have met with representatives of the WHO to discuss a potential definition for long covid in children, but none has been established so far. The WHO says it will need more studies and research.
While progress on finding a clinical definition has stalled, there has at least been some agreement over a way to define long covid in children for research purposes.
In February, Stephenson and his colleagues published a definition of long covid in children to be used in research that states that symptoms must follow a confirmed case of covid-19, must impact the child’s life and physical, mental, or social well-being, and must persist for at least 12 weeks. Stephenson hopes the WHO will align its definition with this one, but in the meantime this definition should at least help ensure that researchers are studying the same thing, he says.
The only way to prevent long covid is to avoid contracting SARS-CoV-2, which is why many doctors and scientists encourage people to get vaccinated. It is not clear how much protection vaccines may offer against long covid, but a few recent studies suggest that vaccination can reduce a child’s risk of severe illness from the omicron variant by two-thirds.
Long covid is thought to more frequently follow more severe infections, but it can also follow mild or even asymptomatic cases. “This seems to be more of the case in children, which I think is unique and disturbing,” says Yvonne Maldonado, an infectious disease pediatrician based at Stanford University and chair of the American Academy of Pediatrics’ Committee on Infectious Diseases.
Because vaccinations can reduce the severity of cases, and should reduce transmission, they are recommended for all children over the age of 5 in the US. As of March 30, 58% of 12- to 17-year-olds had received both doses of a covid-19 vaccine, according to CDC data published by the American Academy of Pediatrics. Only 27% of those aged 5 to 11 had.
In the UK, covid-19 vaccinations for young children are the center of another debate. The UK’s Joint Committee on Vaccination and Immunisation (JCVI), which advises the government, announced a plan to offer all children aged 5 to 11 a covid-19 vaccine just last month, and then only on a “non-urgent” basis.
“I think the JCVI have got it right all along,” says Absoud. “The way they’ve left it now is that it’s a choice for families.”
"A hell of a lot of children" are affectedBinita Kane at Manchester University NHS Foundation Trust
Of course, there are other ways to reduce transmission among children. The experts we contacted stressed the importance of keeping schools open, and said that measures such as improving ventilation and air quality, and masking, at least among adult caregivers, during surges of transmission can help keep case numbers down and help prevent both long covid and “long pandemic syndrome.” They are also among the only options we have to protect kids under 5.
All children who are significantly affected by SARS-CoV-2, whether directly or indirectly, will need support to recover, so arguments over the prevalence of long covid in children may be beside the point. “Whether it’s long covid or long pandemic syndrome, everything needs to be treated,” says Villapol.
Even if only 1% of children develop long covid following an infection, the total number of affected children will reach the millions, given how many children have already contracted the virus. The JCVI’s guidance on immunizing children suggests 85% of children in the UK aged 5 to 11 had been infected with the virus by the end of January 2022, before they were eligible for vaccination. “It’s a hell of a lot of children,” says Kane.
Today, Kane’s daughter Jasmin is doing better. A new treatment regime seems to have helped, and while it hasn’t completely restored her energy levels, she is “remarkably improved,” says Kane.
The trouble is, while researchers debate prevalence, the focus is drawn away from biological causes and potential treatments, meaning many other children are still suffering, she says.
“We can’t wait for years,” Kane says. “We need to move on.”
Correction: This story has been updated to clarify the range of estimates of the prevalence of long covid in children.
Biotechnology and health
What to know about this autumn’s covid vaccines
New variants will pose a challenge, but early signs suggest the shots will still boost antibody responses.
A biotech company says it put dopamine-making cells into people’s brains
The experiment to treat Parkinson’s is a critical early test of stem cells’ potential to tackle serious disease.
Tiny faux organs could crack the mystery of menstruation
Researchers are using organoids to unlock one of the human body’s most mysterious—and miraculous—processes.
How AI can help us understand how cells work—and help cure diseases
A virtual cell modeling system, powered by AI, will lead to breakthroughs in our understanding of diseases, argue the cofounders of the Chan Zuckerberg Initiative.
Get the latest updates from
MIT Technology Review
Discover special offers, top stories, upcoming events, and more.