To investigate the short-term effects of the first wave of COVID-19 on clinical parameters in children with type 1 diabetes (T1D) from 82 worldwide centres participating in the SWEET registry.Methods: Aggregated data per person with T1D ≤ 21 years of age were compared between May/June 2020 (first wave), August/September 2020 (after wave) and the same periods in 2019. Hierarchic linear and logistic regression models were applied. Models were adjusted for gender, age-and diabetes duration-groups. To distinguish the added burden of the COVID-19 pandemic, the centres were divided into quartiles of first wave COVID-19 associated mortality in their country.