SARS-CoV-2 infection is generally mild or asymptomatic in children but the biological basis for this is unclear . We studied the profile of antibody and cellular immunity in children aged 3-11 years in comparison with adults . Antibody profiles in children were strong with high titres against spike protein and receptor binding domain (RBD). SARS-CoV-2 seroconversion in children strongly boosted antibody responses against seasonal beta-coronaviruses, partly through cross-recognition of the S2 domain, indicating a broad humoral response that was not seen in adults . T cell responses against spike were also> 2-fold higher in children compared to adults and displayed a strong Th1 cytokine profile . SARS-CoV-2 spike-reactive cellular responses were present in more than half the seronegative children, indicating pre-existing cross-reactive responses or sensitization against SARS-CoV-2 . Importantly, all children retained high antibody titres and cellular responses for more than 6 months after infection whilst relative antibody waning was seen in adults . Children thus distinctly generate robust, cross-reactive and sustained immune responses after SARS-CoV-2 infection with focussed specificity against spike protein . These observations demonstrate several novel features of SARS-CoV-2-specific immune responses in children and may provide insights into relative clinical protection in this group . Such information on the profile of natural infection will help to guide the introduction of vaccination regimens into the paediatric population.