Chinese medics in Shanghai were given Covid-19 inoculations this week, as vaccine makers insisted their jab was effective against current virus mutations.

China is racing to vaccinate millions ahead of the country's Spring Festival travel rush.

Pharma giant Sinopharm was given "conditional" approval for its vaccine candidate last week, and makers said they were confident the vaccine was effective despite a new variant strain spreading rapidly.

The "current mutation of the Covid-19 virus has not been able to make the vaccine ineffective", Yang Xiaoming, president of the group's China National Biotec Group subsidiary, told state broadcaster CCTV on Monday.

Vaccination programmes are being rolled out for key groups across China, state media reported, such as workers in community roles, logistics or food sectors.

Unlike the approach taken in many European countries, China is only vaccinating those aged between 18 and 59.

The state-run Global Times newspaper quoted unnamed industry observers who said the ratio of elderly volunteers was small in the vaccine clinical trials, which explains a "cautious use of vaccination among elderly people at present".

The vaccine -- which Sinopharm says has a 79 percent efficacy rate -- requires two doses with an interval of two to four weeks.

"A vaccine dose has a number, just like an ID card," Yang told CCTV.

"This ID card can help us find its source and its past manufacturing process all the way from the raw materials."

In February, the world's largest human migration sees hundreds of millions of people travel across China to celebrate the Lunar New Year with their families.

Authorities said more than 73,000 people including bus drivers and community workers have already been vaccinated in the capital Beijing, where AFP saw people queuing at vaccination centres to receive their shot.

China has largely brought the virus under control through strict lockdowns and travel restrictions, and its borders are still effectively closed to most foreigners.

But there have been a series of local outbreaks in recent weeks.