What all of these early studies lacked was a control group. They included only children who reported having had Covid-19. This was a crucial limitation. Until these children could be compared to others who did not report having Covid-19, it was impossible to know whether their symptoms, like fatigue and poor sleep, were due to the virus or to the general stresses that children have been enduring during the pandemic — or even to chance.

Over the last two years, experts’ understanding of long Covid in children has deepened. Several peer-reviewed studies now include control groups consisting of children who did not have Covid-19 but who have lived through the same pandemic conditions — loneliness, interrupted schooling, anxiety, tensions at home, the loss of loved ones, and the like.

These studies indicate that long Covid in children is rare and, when it does occur, is short-lived. In one study, 97% of children ages 5 to 11 with Covid-19 recovered completely within four weeks. In the small group that had bothersome symptoms after four weeks (usually loss of smell or fatigue), most had fully recovered by eight weeks.