This isn't exactly news, is it?
The main concern has always been that the kids may get a sniffle or even nothing visible, then spread it around like they do with all other bugs (not blaming them, just stating facts)
... And the adults around them (you know, "unimportant" people caring for these kids, like parents, teachers, grandparents...) catch the illness and end up bedridden for weeks, or even in hospital (many teachers/parents are over 40), and possibly die.
Anyone who genuinely cares for kids would be horrified at this prospect for the kid's sake (not just the adults in their lives)
And yet some people insist on constantly deflecting this very legitimate concern with "oh, but kids don't get ill too badly, look at these studies" (by the way, just because the kids don't get hospitalised doesn't mean they don't get poorly, with fever, pain, etc.)