Rather than doing napkin math using sources like joinzoe, i.e. self report (app) on population with high natural immunity due to uncontrolled spread, with great health care infra, and low population density - many factors why that's a bad place to start your reason chain - here's earlier study by epidemologists who are familiar with PRC conditions.
https://www.nature.com/articles/s41591-022-01855-7
> lift such measures could see more than 112 million symptomatic cases of Covid-19, five million hospitalisations, and 1.55 million deaths.
There's also later analysis that extrapolates with TW/SKR numbers after they began living with covid with IIRC greater deaths. These are fellow East Asian examples with more simliar conditions than PRC except they have much better per capita health care infra.
>relevant factor is how good is the vaccine at preventing major illness and hospitalisation.
Yes and the relevant factor to that relevant factor is PRC doesn't have the ICU beds / hospital infra per capita to absorb even vaxed spread. Most of country is old and underdeveloped and "crushing the curve" is still the best path. Vax prevents severe cases but at PRC scale and infectiousness of omicron, in dense urban enviroments during colder seasons, that's still more symptomatic severe cases than the medical system can handle.
>We find that the level of immunity induced by the March 2022 vaccination campaign would be insufficient to prevent an Omicron wave that would result in exceeding critical care capacity with a projected intensive care unit peak demand of 15.6 times the existing capacity
https://www.theguardian.com/world/2022/may/11/lifting-zero-c...
That's the crux of the issue, PRC is a developing country with low hospital beds per capita that demographically skews old (and antivax). These factors means PRC is better off with no vaccines and zero covid than vaccines and living with covid until zero covid or some other factor makes zero covid unsustainble.