Nearly a million people have taken an experimental coronavirus vaccine developed by Chinese company Sinopharm, the firm said, although it has not yet provided any clear clinical evidence of efficacy.

China has been giving experimental Covid-19 vaccines to people including state employees, international students and essential workers heading abroad since July.

Sinopharm's chairman told media this week that nearly a million people have now received their vaccine for emergency use, though he did not provide a specific figure.

"We have not received a single report of severe adverse reaction, and only a few had some mild symptoms," Liu Jingzhen said in an interview re-published by the state-owned firm on Wednesday.

China has been bullish about the development of its vaccine for the new virus -- which first emerged in the centre of the country late last year -- with four vaccines now in late-stage testing.

Many of the trials are taking place overseas, as China has largely brought the virus under control within its borders.

Sinopharm is testing two vaccines in late-stage trials in countries including the UAE, Bahrain, Egypt, Jordan, Peru and Argentina.

The company claimed this week to be "leading the world in all aspects" of vaccine development, although it did not offer clinical evidence from ongoing trials.

Instead it cited anecdotal experiences from those who have been inoculated, including "construction personnel, diplomats, and overseas students" who it said have gone on to visit more than 150 countries after vaccination without being infected.

President Xi Jinping has declared that any Chinese vaccine would be a "global public good", after the country came under criticism, particularly from the US, for its early handling of the outbreak.

Many who have been inoculated in China are not formal participants in drugmakers' trials and are said to have done so voluntarily.

Competition has intensified among pharmaceutical companies racing to develop a Covid-19 shot, with two vaccines -- one by US company Pfizer and its German partner BioNTech, and another by US firm Moderna -- publishing large-scale trial data this month that showed their jabs were around 95 percent effective against Covid-19.

Fauci says Pfizer, Moderna vaccine data is 'solid'

The United States' top infectious disease official said Thursday that two coronavirus vaccines being tested were "solid," and that the speed at which they were developed has not compromised safety or integrity.

Anthony Fauci spoke at a rare briefing from the White House virus task force to reassure some public concerns about the two vaccines -- one from Pfizer/BioNTech and the other by Moderna -- after both companies announced successful trials.

"The process of the speed did not compromise at all safety nor did it compromise scientific integrity. It was a reflection of the extraordinary scientific advances in these types of vaccines which allowed us to do things in months that actually took years before," he said.

And he sought to address fears that the vaccine announcements may have been politically driven. 

"It was actually an independent body of people who have no allegiance to anyone -- not to the administration, not to me, not to the companies -- that looked at the data and deemed it to be sound," he said.

Next the data will be carefully examined by the Food and Drug Administration, he said. BioNTech has said it will apply to the FDA for emergency use authorization by Friday. 

"So we need to put to rest any concept that this was rushed in an inappropriate way. This is really solid," Fauci continued. 

The BioNTech/Pfizer and Moderna shots have taken the lead in the global chase for a vaccine, after large-scale trial data this month showed that their jabs were around 95 percent effective against Covid-19.

The twin breakthroughs have lifted hopes for an end to a pandemic that has infected more than 56 million people and caused more than 1.3 million deaths worldwide since the virus first emerged in China late last year.