It does seem high. I read recently that the Chinese vaccines had about a 50% efficacy rate in preventing disease..they published no studies and data was from what happened in areas it was used. The good news it still greatly decreased hospitalization and death.

The rna vaccines by Pfizer and Moderna had much great higher protection rates but the work was done prior to some new variants. Though they say it is protective against those variants it’s not clear that it is absolutely effective in preventing infection.

AsteaZeneca vaccine is closer to the Chinese vaccines in its development but was throughly tested. I forgot the trials but I think it was in the 70-80% area on the first iteration of Covid. My guess would be it is a good vaccine that is between the Chinese and mRNA vaccines in efficacy. So though there might be more breaks in protection it quite likely will prevent most severe cases and death.