The study is reasonably large (N=1355) and looks well performed. Among seropositive and seronegative 6-16-year-old children, 9% vs. 10% reported at least one symptom beyond 4 weeks, and 4% versus 2% at least one symptom beyond 12 weeks.
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— Prof Francois Balloux (@BallouxFrancois) July 1, 2021