As the coronavirus pandemic has spread, speculation grew that children may be less susceptible to COVID-19, since so few appeared to get sick or end up in the ICU.
But a new peer-reviewed study conducted in China — the largest to date — suggests many children do get sick, often without displaying clear coronavirus symptoms, and a minority of children develop severe or critical infections.
The World Health Organization cautioned parents to prepare to safeguard their children against the coronavirus, citing the study.
"What we need to prepare for is the possibility that children can also experience severe disease," Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, told reporters Wednesday.
An early and non-finalized version of the paper, published by the journal Pediatrics, was released on Tuesday, after peer-review and ahead of the official publication date, because the editors felt it was too urgent to wait.
The researchers from various Chinese universities looked at data on more than 2,000 pediatric patients across seven provinces in China who were diagnosed with the coronavirus between January 16 and February 8, with a median age of seven years old.
They found 90% of the children were either asymptomatic or had mild or moderate COVID-19 symptoms, including 39% who developed pneumonia without showing obvious symptoms, around 50% who developed a fever, fatigue, sore throat, cough, or shortness of breath, and 4% who showed no symptoms at all.
However, a 6% of children developed critical or severe infections, including one 14-year-old boy in Hubei province who died of COVID-19 infection.
Infections were most severe in the youngest children: the Chinese Center for Disease Control and Prevention recorded severe infections in just over 10% of infants, 7% of kids aged one to five years old, 4% of six- to 10-year-olds, 4% of 11- to 15-year-olds, and 3% of older teenagers.
"Although clinical manifestations of children's COVID-19 cases were generally less severe than those of adults' patients, young children, particularly infants, were vulnerable to infection," the researchers wrote. "Furthermore, this study provides strong evidence for human-to-human transmission."
The researchers are unsure why COVID-19 infection is less common in children, and many do not display symptoms
Children had less severe COVID-19 overall compared to adults, and the researchers are unsure why that is, but the researchers suggested kids may, generally, be sheltered from the virus.
"This may be related to both exposure and host factors," the researchers wrote. "Children were usually well cared for at home and might have relatively less opportunities to expose themselves to pathogens and/or sick patients."
They also theorized the since children tend to get more colds and respiratory infections in the winter months than adults, the children may more antibodies to protect them against severe COVID-19.
Either way, experts say, the study shows the importance of thinking about children when implementing shutdown measures to control the virus, as many governments question whether or not to close schools and how to deal with the issue of childcare.
"If they do develop symptoms, they could indeed transmit the virus to others either during their preclinical period or once the symptoms begin," Lee W. Riley, MD, in the infectious diseases department at the University of California at Berkeley, who was not involved in the study, told Business Insider. "How much they contribute to the overall transmission events in a community is unclear at this time."
There were caveats to the study. Though it did include data on children across China, not just in the epicenter, it's possible these results will not translate to other countries affected by the coronavirus, and, for that reason, the researchers said more research is needed before we can draw clear conclusions about how children are affected.
- Read more:
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- Many coronavirus patients are passing the virus before showing symptoms, a new study found — yet another reason for social distancing
- The coronavirus can be spread from person to person before someone realizes they even have it, according to the Chinese health minister
- The average coronavirus patient infects at least 2 others, suggesting the virus is far more contagious than flu
