> over the long run the set of all COVID-19-naive individuals becomes dominated by the very young (infants/toddlers), who have essentially zero risk of COVID-19 mortality.
"Babies under 1 year old and children with certain underlying conditions may be more likely to have severe illness from COVID-19."
Zero risk?
BTW they generally become less deadly because the less deadly spread faster because they don't kill the host, but this virus has a rather long incubation period, so you can have both. Easy spread and higher death rate.