That’s not what they are actually saying. They are not barring anyone. They are just limiting their recommendation to people over 50, and certain other groups, see below.
Google translate of the Denmark health ministry web page:
1. Who will be offered vaccination against covid-19?
People aged 50 and over are offered vaccination.
People who are under 50 years of age and who are at increased risk of a serious course of covid-19 will also be offered vaccination against covid-19.
Personnel in the health and care sector as well as selected parts of the social sector, who have close contact with patients or citizens who are at increased risk of a serious course of covid-19, will also be offered booster vaccination against covid-19.
In addition, we recommend that close relatives in the same household as persons with severely weakened immune systems take up the offer of vaccination to protect their relatives at particularly increased risk.
Well, it is a step in the right direction. The foolishness of recommending or mandating an experimental drug whose long-term side-effects CANNOT be known to people of exceptionally low risk of severe disease is a Shakespearean tragedy.