https://www.bbc.com/news/world-asia-china-56713663
Gao Fu, head of the Chinese Centres for Disease Control and Prevention, on Saturday said at a conference the current vaccines "don't have very high rates of protection".
He suggested that the China was considering mixing Covid-19 vaccines, as a way of boosting efficacy.
Mr Gao explained that steps to "optimise" the vaccine process could include changing the number of doses and the length of time. He also suggested combining different vaccines for the immunisation process.