Are China's vaccines not as good as the others?

What does efficacy mean?

"It's important to understand firstly, what that outcome measured," said Professor Fiona Russell from Murdoch Children's Research Institute, University of Melbourne.

She pointed out that a vaccine with an efficacy of about 50% in a trial means that there was a 50% reduction in the cases that they were measuring.It doesn't mean that all those people will get sick, but just means it halves the rate and risk that people may get infection.

Therefore the efficacy numbers really just tell you what happened in each vaccine trial,not exactly what will happen in the real world.