To the best of our knowledge, no longitudinal study has reported the kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses in children. Here we report the results of the second round of antibody testing in children from a prospective multicentre cohort study in the UK. The protocol and initial results are available elsewhere.1,2 Recruitment took place between April 16, and July 3, 2020, at five UK sites (Belfast, Cardiff, Glasgow, London, and Manchester) and included healthy children aged 2–15 years. Follow-up visits at all five UK sites took place between June 26, and Aug 15, 2020.