Brazil reported that their trials showed that the Chinese vaccine they were planning to buy was only just effective enough to be worth using, & greatly inferior to the western vaccines tested in Brazil.
It seems that not all Chinese vaccines are equal.
Not all western vaccines are equal either, of course, but those that perform poorly in trials are abandoned. That's happened to a couple of covid-19 vaccines that I've heard of.
Are you referring to the news from last year that Sinovac's Coronavac has a 50.4% efficacy at preventing symptomatic infection? While that study is valid, keep in mind that the same study and others from Chile found that the vaccine reduces the probability of severe sickness requiring hospitalization by some 85% and likewise for the mortality rate. Indonesia also reported similar figures later. The links should be in this thread back around July 2021 or thereabouts so I am not going to repeat it. Chile's number also suggests a higher efficacy of some 60% at preventing symptomatic infection but I think we all agree that it isn't as good as the mRNA vaccines.
However, suggesting that China should have adopted a Western vaccine fails to recognize that there wasn't enough Western vaccines for the West back then, much less for the rest of the world. From our own experience (Indonesia) China was able to supply us with Coronavac as early as January 2021. Meanwhile the first shipment of Pfizer's Cominarty arrived in August 2021. Astrazeneca's Vaxzevria arrived reasonably early in March 2021 but the numbers were in the million doses when Coronavac were in the tens of millions. Extrapolating from that to a hypothetical where China were to abandon their own COVID-19 vaccines and get Western ones, it should be obvious that there will be a far more severe shortage than what we experienced. China had no mRNA vaccine production facility at the time, so they can't simply license mRNA vaccine and make them themselves. I am less clear on their ability to make hybrid adenovirus vaccine like Astrazeneca's, but even if they can license and manufacture that, it means leaving the production capability for inactivated virus idle. Some of the equipment are likely usable for other vaccines but it's safe to say that China (and the rest of the world) would have had hundreds of millions less vaccine doses had China adopted a Western vaccine only approach.
China today can also make their own mRNA vaccine (Walvax's AWCorna) which according to Indonesian clinical trial has a 83% efficacy rate
, which is not as good as Western mRNA vaccine but is a significant improvement over inactivated virus ones. But I am not aware of a massive deployment of this vaccine in China yet.
Anyway, given all of the above I think China's problem isn't so much their lack of use of Western vaccines. That was just impossible at the time. Rather, as has been pointed out, they don't have an exit ramp. They were banking of Zero COVID policy to get them by until the virus is gone, but the virus is staying. So even if they managed to get rid of the virus domestically, it will just re-enter again from the rest of the world. And China can't close themselves tight enough anyway. North Korea has way less contact with the outside world and they still can't prevent the virus from getting in. China has a semi-porous border with Myanmar (they can officially close the border but smuggling still happens). China should try to figure out how to adapt to an endemic situation. Manage things so while infections do happen the number of hospitalizations are few and deaths even fewer. This does require admitting that the Zero COVID approach doesn't work and that's probably what they won't do. CCP has this issue of not being able to admit they're wrong unless they can blame the previous leader.