They are already doing that and it will take some time. However no vaccine is 100% effective against mortality. Bear in mind that China had almost no covid deaths post-2020. Any covid death now is considered a failure as it would have been "preventable" under a strictly zero covid policy.

This is why the figures out of China is looking too good to be true right now with 150K+ recent cases, very low intensive care admission and only 2 deaths so far(both had very serious underlying conditions including end stage renal failure and cerebral infarction). One might argue that the officials have an incentive to hide the true figures to save face, but keeping the numbers low does not necessarily make them look any better as the lockdown appears overly harsh and disproportionate to the risks. The only options is to try and return to the zero covid days, no plan B allowed.