Denmark, which has an excellent health infrastructure including data collection, banned under-18s from being vaccinated and in mid-September the ban was extended to boosters for under-50s, other than in exceptional circumstances for immunocompromised and high-risk individuals in both cases.
The explanation offered by the health authorities is interesting both for what they said and what they did not say. They anticipate a rise in Covid-19 infections over autumn and winter and “aim to prevent serious illness, hospitalisation and death.” This risk applies to 50-year olds and above and not those younger. Because the vaccines are not meant to prevent infection, they will no longer be offered to the under-50s.
However, governments don’t ban products merely because they are not beneficial. Bans apply only to products that inflict harms. So the unstated reality is the benefit: harm ratio is no longer favorable.