Explain to me if practically the entire adult population is vaccinated what else can be done
This:
1. Vaccinate teenagers (and possibly younger children too, in due course). The UK is being too slow (slower than other European countries) at getting teenagers vaccinated, and we are paying the price in the rate of infection.
2. Require people to show vaccine certificates or proof of a negative test when going to events, pubs, restaurants etc. Other countries are doing that and are reaping the benefits in lower infection rates.
The reason we are suffering such high infection rates is simply because our dear leader is being held hostage by his libertarian right wing, who are opposed in principle to sensible precautions.