Those rates are pretty disastrous - the US have "only" managed 85% in their over 75s, and that's been a massive problem for them .
Countries like the UK, Denmark, Spain, Ireland are well over the 95% mark (pushing 100% in most areas) in these older groups. That immunity gap means massive potential hospitalisations/deaths as the infection rate rises - even with the Omicron variant.
For HK you'd be looking at something worse than the US ratios, given the lack of immunity (vaccine induced or from past infection) in the most vulnerable. You can get an idea of how much the vaccines and boosters have mattered in this Twitter thread.