Long COVID in children and young people: then and now.

On 11 March 2020, the WHO characterized COVID-19 as a pandemic. A clinical case definition for post-COVID-19 condition in children and adolescents by expert consensus was agreed by the WHO in 2023. It is now 5 years since the WHO declared a pandemic, and this review aims to summarize key advances in our understanding of long COVID over those 5 years. That symptoms could persist in adults and CYP for months after initial infection was first reported in Autumn 2020. Long COVID in adults is frequently characterized by symptoms of fatigue and breathlessness but brain-fog, joint and muscle pain have been reported much more commonly in adult follow-up than CYP. The most common persisting symptoms experienced by CYP after COVID-19 infection in initial studies, often with less than a year of follow-up, were fatigue, headache, shortness of breath and persisting loss of smell and taste. With longer follow-up, up to 2 years, the commonest symptoms still include not only fatigue, headache and shortness of breath but also sleep difficulties, whereas loss of smell and taste persisted only in a minority. However, many symptoms were almost as common in test-negative controls, raising questions about the causal role of SARS-CoV-2 virus. Predictors of long COVID, as defined, were female sex, history of asthma, allergy problems, learning difficulties at school and family history of ongoing COVID-19 problems. The implications of the findings for clinical practice and research are that long COVID is not the same in CYP as adults; both their physical and mental health should be studied; and intervention trials are needed.