BEIJING, June 20 (Xinhua) - More than 1 billion doses of COVID-19 vaccines had been administered in China by Saturday, as the country is pushing ahead with the largest vaccination drive in the history of New China.

It took the country just five days to hit its most recent 100-million dose increase, according to daily updates by the National Health Commission (NHC).

China accelerated its pace of free COVID-19 vaccinations for the whole nation since late March. It took China 25 days to climb from 100 million doses to 200 million doses, 16 days to increase from 200 million to 300 million, and six days from 800 million to 900 million.

A total of 21 COVID-19 vaccines have entered clinical trials in China since last year. So far, four vaccines have been granted conditional marketing approval and three have been authorized for emergency use within the country.

China's nationwide vaccination campaign is open to people aged over 18. The country has approved the emergency use of domestic inactivated vaccines on people aged 3 to 17. Detailed policies will be formulated for the inoculation of this age group based on the specific COVID-19 situation.

At least 70 percent of the target population in China is expected to be vaccinated against COVID-19 by the end of this year, according to Zeng Yixin, deputy head of the NHC.

The large-scale vaccination campaign carried out across China has shown that Chinese COVID-19 vaccines are safe, said Zeng, noting that the incidence rates of common side effects and abnormal reactions caused by the COVID-19 vaccines were both below the average figures reported by various vaccines included in the country's regular vaccination plans in 2019.