The healthier and more developed your immune system the more ill you will become if infected. 20 to 50 year olds are more at risk.
The irony is surprising.

That may have been true of the 1918 flu pandemic but so far as is known statistics on corona virus suggest fatalities are concentrateed among the old with pre existing conditions.

https://www.newscientist.com/article/2233269-how-bad-is-the-covid-19-coronavirus-outbreak-likely-to-get/