Washington (AFP)
The American company Moderna announced on Tuesday that it had started trials of its Covid-19 vaccine on thousands of children aged 6 months to 11 years, a new step considered necessary to arrive at an end to the pandemic.
If they constitute a significant part of the population, children are however less exposed to severe cases of the disease, while transmitting it less for the youngest among them.
Their vaccination has thus far not been a priority.
Currently, Pfizer's Covid vaccine is licensed for people aged 16 and over, and Moderna and Johnson & Johnson's for those 18 and over.
The three American companies have already started, sometimes for several months, clinical trials to test their vaccine on adolescents (from 12 years old).
AstraZeneca, for its part, is studying the effect of its vaccine from the age of 6.
Biotech company Moderna now expects 6,750 children and babies to participate in trials in the United States and Canada.
They will be followed for 12 months after the second injection.
Their number is less than the tens of thousands of recruits for trials on adults, because the main point here is to determine which dosage is best suited for them, experts explain.
The mechanism of the vaccine itself, as well as its safety, have already been studied.
According to well-respected immunologist Anthony Fauci, American children under the age of 12 will "very likely" be vaccinated in early 2022, he said last month.
- "High priority" -
"I consider this to be a high priority," said Dr. Lee Savio Beers, president of the American Academy of Pediatrics, to AFP.
"Children under 10 transmit the virus less, but that does not mean that they do not transmit it at all", including to people at risk, she argued.
And "even if they are less likely to fall terribly ill, they can also be", including sometimes over several months, she said, recalling that several hundred deaths of children have been recorded.
In addition, they are "disproportionately affected" by certain consequences of the pandemic, such as school closures.
"The more people we can vaccinate, the better it will be," said Henry Bernstein, professor of pediatrics.
In the United States, about a fifth of the population is under the age of 18.
And this proportion may be higher in other countries.
It therefore also seems unlikely that the so-called collective immunity, necessary to stop the epidemic, can be achieved without including the youngest.
We do not yet know exactly what percentage of the vaccinated population will be necessary to achieve this collective immunity: perhaps between 70% ... or 85%, according to Dr. Fauci.
- Necessary for collective immunity -
"Effective herd immunity will require vaccination of children," pediatric specialists Perri Klass and Adam J. Ratner wrote in the prestigious scientific journal NEJM in February.
This is an "ethical obligation and a practical necessity", they say.
The benefits will be both "direct" (children will get less sick) and "indirect" (they will not transmit the disease), they stress.
However, "the calculation of the risk / benefit ratio will be different when you vaccinate a child of 9 years or someone of 90 years", nuance with AFP Amesh Adalja, of the Johns Hopkins Center for the health security.
What vaccines are very effective against, namely severe cases of Covid-19, hospitalizations and deaths, "are very rare when you consider the younger population."
In this context, "what level of side effects is tolerable?", He asks, advancing the idea of a distribution by age groups, which would prioritize older adolescents over small children.
Because they haven't finished their development, clinical trials in children aim to understand how their immune systems respond to different stages of growth.
Proceeding in stages, gradually descending the age groups, is a standard approach in the development of treatments.
But according to Amesh Adalja, it is also possible that the pandemic will be under control even before the distribution of vaccines for children is successful.
© 2021 AFP