AIM: The 2019 coronavirus disease (COVID-19) has spread worldwide and the number of cases continues to rise exponentially Epidemiologic reports indicate that severity of illness increases with age However, the reasons behind the relative protection of children and infants are unclear Whether the rationale is host-related or virus dependent is important to determine since the latter could change with viral mutations We review factors that could affect the susceptibility of children to the novel coronavirus

METHODS: We search publications indexed on PUBMED

RESULTS: Descriptions of the pathophysiology of current and previous coronavirus infections suggest several viral targets and immunomodulatory pathways affecting the severity of illness There is limited evidence to suggest age-variability of viral cell receptors and transmembrane co-factors required for coronavirus entry and replication However, the ensuing cytokine storm and the effect of higher melatonin in children are age-dependent and could explain decreased disease variability in children

CONCLUSION: We believe that current evidence suggests host factors can play a role in disease severity in children and thus may remain protective despite potential virus mutation in the future However, we recognise and discuss avenues of future research that can further illuminate the reasons children are protected from severe COVID-19 illness