The efficacy of Chinese Covid-19 vaccines is "not high" and authorities are weighing options to bolster protection -- including mixing different shots, China's top disease control official has said.
China's top disease control official has said the efficacy of the country's Covid vaccines is low, in a rare admission of weakness.
In a press conference, Gao Fu added that China was considering mixing vaccines as a way of boosting efficacy.
China has developed four different vaccines approved for public use, though some trials abroad had suggested efficacy as low as 50%.
Mr Gao later said his comments had been misinterpreted.
More than 100 million people in China have received at least one shot of the vaccine.
Beijing has insisted the jabs are effective and said in March that obtaining visas would be easier for foreigners who have received a Chinese vaccine.
Gao Fu, head of the Chinese Centres for Disease Control and Prevention, 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.
With little data released internationally, the effectiveness of the various Chinese vaccines has long been uncertain.
Brazilian trials of the Sinovac vaccine CoronaVac for instance, showed an efficacy rate of around 50.4%, which is barely over the 50% threshold needed for regulatory approval by the World Health Organization (WHO).
Interim results from late-stage trials in Turkey and Indonesia however, had suggested the efficacy rate of the Sinovac shot to be between 91% and 65%.
Western vaccines like the ones by BioNTech/Pfizer, Moderna have an efficacy rate of around 90% or higher while the UK's AstraZeneca jab is thought to be around 76%.
So far, Sinovac's CoronaVac jab has only been fully authorised for use by China.
But Beijing is also offering its vaccines around the world and has already shipped millions of doses to a number of countries.
In Asia, the biggest takers are Indonesia, Malaysia, the Philippines, Thailand and Pakistan, while in the Americas, Brazil, Mexico, Chile, Colombia and Ecuador have also ordered millions of shot.
In Europe, Turkey and Ukraine have signed large contracts for CoronaVac.
The vaccine is thought to be particularly important for African countries where so far Zimbabwe, Somalia, Djibouti, Benin and Tunisia have received vaccines from China.