The Chinese Centre for Disease Control and Prevention (CDC) said four COVID-19 vaccines were now in the final stage of clinical trials. At least three of those have already been offered to essential workers under an emergency use programme launched in July.

CDC chief biosafety expert Guizhen Wu said phase 3 clinical trials were proceeding smoothly and the vaccines could be ready for the general public in November or December.

She said: “So far, among the people who were vaccinated, no one has been sick with the disease.

“So far, the vaccination scheme works very well. No side effect occurred.”

Ms Wu, who said she has experienced no abnormal symptoms in recent months after taking an experimental vaccine herself in April, did not specify which vaccines she was referring to.

A unit of state pharmaceutical giant China National Pharmaceutical Group (Sinopharm) and US-listed Sinovac Biotech are developing the three vaccines under the state’s emergency use programme.

A fourth COVID-19 vaccine being developed by CanSino Biologics was approved for use by the Chinese military in June.

Sinopharm said in July its vaccine could be ready for public use by the end of this year after the conclusion of Phase 3 trials.

Global vaccine makers are racing to develop an effective vaccine against the virus which has killed more than 925,000 people.

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But China’s approach has raised concerns among many Western countries with experts warning against authorising the emergency use of vaccines that have not completed testing.

Anna Durbin, a vaccine researcher at the Johns Hopkins University in the US, described China’s emergency use programme as “very problematic”.

She said it was impossible to judge efficacy without a clinical trial standard control group.

She said: “You’re vaccinating people and you don’t know if it’s going to protect them.

“Recipients of the experimental vaccines could eschew other protective measures.”

The National Health Commission said in a statement that all of the new cases were imported infections involving travellers from overseas.

The number of new asymptomatic infections rose to 16 from nine a day earlier, but China does not count them as confirmed cases.

The total number of confirmed COVID-19 cases in the mainland now stands at 85,214, while the death toll remains unchanged at 4,634.