Repeat COVID infections may be more serious for kids than previously believed.A large, NIH-funded study found children and adolescents were twice as likely to develop long COVID after a second infection compared with a first.Researchers reviewed electronic health records from more than 465,000 young people between January 2022 and October 2023, when Omicron was the dominant variant.According to the results, the risk of myocarditis – a dangerous inflammation of the heart muscle -- tripled after a second infection. And blood clots were more than twice as likely.Kids were also found to be at increased risk for kidney damage, abnormal heart rhythms, headaches, abdominal pain, and severe fatigue after getting COVID twice.The authors say these findings challenge the popular perception that COVID is always mild in children and that repeat infections are less concerning.One author says, “More vaccines should lead to fewer infections, which should lead to less long COVID.”The researchers plan to keep tracking children to see if newer variants alter the risks and to test strategies that may help prevent long-term complications.Source: Lancet Infectious DiseasesAuthor Affiliations: Ann and Robert H. Lurie Children's Hospital of Chicago, Perelman School of Medicine at the University of Pennsylvania.Sign up for our weekly HealthDay newsletter