It's too early to say with reliable data. We will definitely know in 2-3 weeks with data from many European countries. In Italy, it looks like the percentage of younger hospitalised people is 12%, but growing.
12% of _COVID ICU patients_ in Italy are below 50 years old. Note that this doesn't let us answer the question of how common are ICU cases among young infected people.
The overall hospitalization rate is difficult to know, due to the huge inaccuracies in the case numbers.