It would seem that Chinese vaccines are hilariously garbage. Just as one'd expect from a Made in China product.

China hoped they could use vaccine exports and cheap deals to build diplomatic reputation. But it turns out that their Sinovac, specifically designed to be halal (Indonesia and UAE loved it), is garbage and doesn't work as intended.
Testing in Brazil earlier showed 50.7% efficacy. But earlier trial results that showed 49.6% efficacy (50% had to be passed to be given an OK – was the number fudged in later stages?) also showed only 35% when including asymptomatic positives.
Chile received a big shipment of Chinese vaccines, which is why it's currently near the top of the most vaccinated countries. But it turned out, after a big outbreak directly following relaxed epidemic measures after vaccination drive, that a single shot was only 3%-16% effective (lol), though after second shot that's supposedly up to 67%.
China, like in so many other technological areas where it likes to use international propaganda to boast about advancement, has used 60s technology and is now suffering comparative shit results.
That China ordered 100M doses of Pfizer back in December already says all you need to know – they don't trust their own product themselves.

https://www.dailymail.co.uk/news/article-9533705/Why-Chinas-bid-woo-world-vaccines-backfiring.html