Table 2.

Potential factors protecting children against severe SARS-CoV-2 infection

Potential protective factor	Mechanisms
Prevention of virus exposure	Early isolation and movement restriction    -Closing schools and day-care centers in epidemics
Appropriate infection handling	Trained immunity (strong innate response) due to    -Live vaccines (BCG, live virus vaccines)    -Frequent virus infections High ACE-2 expression metabolizing angiotensin-2 Lack of immune-senescence Good lung regeneration capacity
Absence of high-risk factors	Absence of ageing related co-morbidities. Less degree of obesity, smoking
High-risk group    1. Infants (< 1 y)    2. Children with pre-existing illnesses (neurological disorders, chronic lung diseases including asthma, uncorrected heart diseases, and genetic disorders)

ACE-2 Angiotensin converting enzyme -2; BCG Bacille Calmette-Guerin