AGT and viral infectious disease: Other postulations include recurrent exposure of children to viral infections modulating their responses to SARS-CoV-2 [9, 10], the high level of melatonin in children in addition to its anti-inflammatory and oxidative properties (inhibiting SARS-CoV-2 infection through the blockage of the CD147 receptor) [25–27], exposure to live attenuated vaccine (BCG, OPV) [28–31], and low expression and function of the angiotensin 2 (ACE2) receptors [32, 33].