https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6119719/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701921/
And then extremely anecdotally: the only people I personally know who have gotten sick† in my ~25–35-year-old social circle have been guys who are, as they say, “on the bike”. Geared up, if you know what I mean.
†and they’ve all recovered well; they had about a week of pretty nasty flu-like symptoms, but then bounced back with bed rest