BEIJING (REUTERS) - China is facing growing difficulties in expanding its mass Covid-19 vaccination drive, but it will continue to inoculate more people and step up the programme of booster shots, a health official said on Friday (Sept 3).

Mr Zheng Zhongwei, an official at the National Health Commission, did not specify the obstacles but stressed that those who have not been vaccinated could not rely on being protected by those who have had the shots, amid concerns over the highly transmissible Delta variant.

"Recently, as (pushing vaccinations) came to the later stage, it has become increasingly difficult," Mr Zheng said at a health forum.

He said China has given full doses to about 900 million people, or more than 60 per cent of its 1.4 billion population, but cited some experts saying that China may need a vaccination rate higher than 80 per cent.

China administered around 13 million doses per day on average in July and August, slower than June's daily average of 19 million.

By the end of October, the country is expected to complete giving regular regimen doses to 1.1 billion people, as well as giving booster shots to limited groups such as the elderly and high-risk employees, according to estimates in Mr Zheng's presentation.

Currently, people are recommended to take booster doses of the same type of vaccine technology as their first vaccinations, but more options might be available once studies on using different shots as boosters yield results, Mr Zheng said.

China has supplied one billion doses of Covid-19 vaccines to the rest of the world, Mr Zheng said.

President Xi Jinping said in August that China would strive to provide two billion doses of Covid-19 vaccines to other countries in 2021.