evidence: Overall, kids have been lucky with the pandemic: Although it’s not yet clear whether they are less likely than adults to contract or transmit Covid-19, they are far less likely to get sick. According to the Centers for Disease Control and Prevention, as of August 25 only about 400 children under 18 have died of the disease in the US. And, of the two dozen states reporting in addition to New York City, just 0.1 percent to 1.9 percent of children who tested positive for the virus have been hospitalized. A recent UK study that crowdsourced health information from the public through an app found that only 1.8 percent of children with Covid-19 still had symptoms eight weeks after infection. [...] The story may be more complex, though, because children’s immune systems are fundamentally unlike those of adults, in ways that are still under study. Scientists know, for example, that the novel coronavirus isn’t the only pathogen to prove much less harmful to children. Adults tend to get much sicker from diseases like hepatitis and mumps; kids with hepatitis often show no symptoms at all.