Comments by Donald Trump that children are “almost immune” to Covid-19 and their immune systems are “much stronger against it,” led Facebook to censor the video for disinformation.
The term “nearly immune” is scientifically vague. What studies have confirmed since the start of the pandemic is that children are at low risk of becoming seriously ill from Covid-19, and are probably less likely to be infected.
But there is no consensus on the question – crucial at the time of the start of the school year – of their contagiousness, once they have contracted the virus, even if they have no symptoms.
What we know: children rarely get very sick
People under 18 represent around 2% of hospitalizations and much less than 0.1% of deaths linked to Covid-19 in the United States, according to the Centers for the fight against diseases (CDC), while they represent 22% Population.
45 child deaths have been attributed to the coronavirus since February in the United States – against 105 for the seasonal flu, and 13,000 deaths from all causes in this age group.
A study, carried out in China at the start of the pandemic on 2,143 cases, shows that 94% of children had no symptoms or mild or moderate symptoms (infection of the lungs, fever, cough but no shortness of breath).
Children who become seriously ill often seem to have a medical history. In Chicago, the ten children hospitalized in March and April all had existing pathologies or co-infection.
All of this is not to say that they are immune, as the onset of severe, but very rare inflammatory disease has revealed.
A thousand cases of this new “multisystemic inflammatory syndrome” have been identified in children around the world, with 2% mortality. Six children have died in the United States, according to the CDC.
What is less certain: are children less infected?
If there are fewer sick children, is it because their bodies fight infection better, or because they contract the coronavirus less? We cannot trust the official number of cases to know the true number of infected children, as the tests have prioritized patients with symptoms, where children are under-represented.
But several quality studies tip the scales in favor of the second hypothesis: the virus seems to infect children less, especially those under 10 years old.
Testing campaigns, in Iceland, Spain, Geneva or in the village of Vo in Italy, recruited representative samples of the population to see the rate of people infected or having developed antibodies to the coronavirus: children were there proportionately less affected than adults.
But the scientific community has not yet reached a consensus. In the United States, a study was launched in May on 2,000 families to find out the real impact of Covid-19 on children.
“We should have answers, with a good study, by the end of December 2020,” said Anthony Fauci, director of the National Institute of Infectious Diseases recently.
What we do not know: are children less contagious?
This is the most pressing question as the start of the school year approaches. If children, even little or no symptoms, are as contagious as adults, then they can be formidable vectors and infect teachers, bus drivers, families …
But assessing a person’s contagiousness is not easy.
A first method is to look at the viral load, or the concentration of virus. A study of 145 children in Chicago showed that children under five had 10 to 100 times more virus particles in their nose, compared to older children and adults. Potentially, that would mean they expel more virus with each breath and infect more people around them, but if that’s established for other viruses, it’s not clear for the new coronavirus.
The other method is epidemiological.
On the one hand, spectacular clusters have erupted in a summer camp in Georgia in the United States, or in a school in Jerusalem and others in Israel, showing that the virus can actively circulate among young people.
But conversely, a large study in South Korea, and others, has shown that children, especially younger ones, rarely infect their loved ones. One of the first outbreaks in France, which started from a chalet in Haute-Savoie, passed through a nine-year-old child who, despite 172 contacts, did not infect anyone.
Many experts also call for distinguishing very young children from adolescents, the latter seeming to be more assimilated to adults.
Finally, a hypothesis is being investigated by immunologists: what if the four common human coronaviruses that cause colds provide immunity against the new coronavirus? Children often have colds, which explains why they are relatively spared from the pandemic. But again, this remains to be proven.