The main receptor that the COVID-19 virus attaches to is known as the ACE2 receptor. This receptor protein is the entry point for the virus to infect human cells. The ACE2 receptor is a normal part of human cells. It is part of a system called the renin-angiotensin-aldosterone system. This system helps regulate bodily functions such as blood pressure, electrolyte balance, and inflammation.
The ACE2 receptor is found in adults throughout the human body, including the lungs, nose, and throat. It is also found in the vasculature (blood vessels) and intestinal tract. However, in children the ACE2 receptor is much less expressed as in the adult body thereby producing few entry points for viral entry. As children become older, the ACE2 receptor presence increases as part of the maturing process. This lack of receptor expression is thought to be protective in children.
Despite children being less vulnerable to the effects of a COVID-19 infection, the are nevertheless still vulnerable. According to the American Academy of Pediatrics (AAP), there have been 4 million cases of COVID-19 among children in the United States, and 330 deaths. This puts the mortality ratio at 0.00825%.
While this is significantly lower than the adult death rate, to say that the death rate is negligible is a poor choice of words. 330 deaths is rare, but not negligible, particularly to the family members of those deceased children.