In this prospective cohort study with 2326 hospitalized children and young people with coronavirus disease 2019 in Spain and Colombia, 36.4% had comorbidities. Asthma, recurrent wheezing, chronic neurological, cardiac and pulmonary diseases significantly increased the risk of severe outcomes such as death, mechanical ventilation and intensive care unit admission. The incremental risk with additional comorbidities underscores the importance of targeted vaccination strategies for vulnerable children and young people populations.