China must think they don't have that and given they have absolute control of the country, nobody will dare to say otherwise.
Thankfully, in democratic countries the best vaccine for the job was chosen.
thats a bit of a white washing job, there was 1000's of posts about the risk/effectiveness of Astrazeneca and the JnJ vaccine that were removed from social media, labeled as misinformation (but were accurate).
The biggest message was "the best vaccine is the first one available", so while we eventually gravitated to Pfizer/Moderna ... it was based on supply and not "the science".
I don't doubt China is hiding info, but America was not exactly a light in the darkness as you're painting it to be.
China cannot change their vaccine of choice (Sinovac) due to political constraints, which is why they are stuck with COVID issues and most of the world have moved on.
The table in this article illustrates it very clearly. At this point in time Pfizer or Moderna are the best choices, unless you want to prolong COVID efforts.
https://news.cgtn.com/news/2021-02-28/COVID-19-vaccines-appr...