Gee, maybe the reason they can't establish a link between Coronavirus and the health of children because the latter are already suffering from a wide variety of auto-immune related disorders...
-NW

An Open Letter to the Director of the National Institutes of Health, Francis Collins: 54% of American Children Suffer from Chronic Health Problems, 1 in 6 has a developmental disorder.
Age of Autism

[snip]

Dear Dr Collins,

I am writing to you about the health catastrophe currently engulfing US children, but not only US children. Just five years ago you gave testimony to Congress as director of the Human Genome Research Institute (HERE):

‘But genes alone do not tell the whole story. Recent increases in chronic diseases like diabetes, childhood asthma, obesity or autism cannot be due to major shifts in the human gene pool as those changes take much more time to occur. They must be due to changes in the environment, including diet and physical activity, which may produce disease in genetically predisposed persons.

Therefore, GEI [Genes and Environment Initiative] will also invest in innovative new technologies/sensors to measure environmental toxins, dietary intake and physical activity, and using new tools of genomics, proteomics, and understanding metabolism rates to determine an individual's biological response to those influences.’

The calamity that we face today is that in 5 years barely a single child has been saved from environmental harm by any government initiative, and new studies report that no less than 54% of US children suffer from the chronic diseases (HERE) and from the CDC itself that 1 in 6 has a developmental disability (HERE), all of which you indicated all that time ago are due to environmental changes.