That age group is too wide to make a meaningful comparison without standardising for age. Less than 10% of under-18s and less than 60% in the 18-24 age group have been fully vaccinated, whereas it's more than 80% for the 55-59 group.

The unvaccinated population in that age group is significantly younger than the vaccinated population. As you would expect, older people tend to die more often.

This is also mentioned in a footnote in the ONS data (and this is why they tend to focus on age-standardised figures).