Depends on what you call "young" - have a look at figure 2 here: https://www.nature.com/articles/s41586-020-2918-0 https://www.nature.com/articles/s41586-020-29

Depends on what you call "young" - have a look at figure 2 here: https://www.nature.com/articles/s41586-020-2918-0 https://www.nature.com/articles/s41586-020-2918-0 For people 35-39 it appears to be 0.01%-0.1%.