For months, some scientists dismissed the lack of symptomatic COVID-19 infections in children as perhaps a factor of schools being cancelled before the pandemic entered its worst phases. But new research has emerged to suggest that children's bodies really do process the virus differently than adults, in a way that makes them less susceptible to its most life-threatening excesses.
In a new study that was reported on by the New York Times yesterday, one reason for children’s relative good fortune is that a branch of their immune system that evolved to protect against unfamiliar pathogens rapidly destroys the coronavirus before the virus can do serious damage to its youthful host.
"The bottom line is, yes, children do respond differently immunologically to this virus, and it seems to be protecting the kids," said Dr. Betsy Herold, a pediatric infectious disease expert at Albert Einstein College of Medicine who led the study. In adults, the body's immune response to the virus is "much more muted".
As the NYT explains, when the body encounters an unfamiliar pathogen, it responds within hours with a flurry of immune activity, called an innate immune response. The body’s defenders are quickly recruited to the fight and begin releasing signals calling for backup. Since children more frequently encounter viruses and other pathogens with which their bodies are unfamiliar, their immune responses are typically a lot harsher than adults'.
Over time, an individual's immune system encounters so many of these biological invaders, that it builds up a large rolodex of frequent pests, then relies on more complicated systems of fighting off bodily threats. At the same time, this 'innate response' fades, leaving adults more susceptible to pathogens that are new to the entire population.
One study examining 60 adults and 65 children and young adults under the age of 24, all of whom were hospitalized at the Montefiore Medical Center in New York City from March 13 to May 17, found that children exhibited severe symptoms much less frequently than even the young adults.
The patients included 20 children with multisystem inflammatory syndrome, the severe and sometimes deadly immune overreaction linked to the coronavirus. Overall, the children were only mildly affected by the virus, compared with adults. The kids mostly reported gastrointestinal symptoms like diarrhea and a loss of taste or smell. Only five children needed mechanical ventilation, compared with 22 of the adults. Only two children died, compared with 17 adults.
To be sure, the coronavirus can be lethal for people of all ages, and there are many risk factors that put people with preexisting health issues at greater risk.
But these differences in immune system function between generations might not be the only reason why kids suffer from COVID-19 in much smaller numbers. Writing in the Blaze, Daniel Horowitz discusses some new research from Europe, which found that 3% of samples of a different coronavirus variety that causes the common cold (between 15% and 30% of colds are thought to be caused by coronaviruses of one type or another) tested positive for COVID-19.
That means a significant number of positive tests from schools and other places children congregate could be false positives. Keep in mind, when a child tests positive, not only are they quarantined for a week, but oftentimes, all children with whom they've been in contact - sometimes even their entire class - are also quarantined for 2 weeks.
But as the world's understanding of the virus improves, maybe societies will learn to allocate resources in a different way that doesn't place so much emphasis on testing and isolating the least vulnerable.