SARS-CoV-2 infection in children - Understanding the immune responses and controlling the pandemic.

In December 2019, a cluster of patients with severe pneumonia caused by a novel coronavirus (SARS-CoV-2) emerged in the city of Wuhan, China. The disease is now termed coronavirus disease 2019 (COVID-19). In the early reports, the patients were mainly middle-aged and elderly men, and children appeared to be less susceptible to this infection. With modern and efficient transportation, the disease quickly spread to almost all corners of the world and the mortality far exceeds that caused by severe acute respiratory syndrome (SARS) coronavirus or Middle East respiratory syndrome (MERS) coronavirus. As the number of children with COVID-19 gradually increases, the disease has been documented in premature babies, infants, children, and adolescents. Severe and fatal cases in children are relatively rare. The burden of disease in children has been relatively low, but the high proportions of asymptomatic or mildly symptomatic infections in children deserve careful attention. A clear understanding of the immune responses to the virus in children and the transmission potential of asymptomatic children is of paramount importance for the development of specific treatments and vaccine in order to effectively control the ongoing pandemic.