The vaccination, available at 48 designated clinics in 15 districts, began on December 24, targeting certain groups of people aged between 18 and 59 years.
The vaccination programme will also cover those who plan to work or study in counties and regions with medium or high risks of exposure to the virus.
The US has accused the WHO of siding with China on the outbreak of the virus, alleging the health body misled the world resulting in over a million deaths.
China has been focusing on developing five types of vaccines, and each method has at least one entering clinical trials.
Coronavirus: Chinese domestic civil aviation returns to normalcy, expects full recovery by September
In the second week of August, domestic arrivals at Chinese airports reached 86 per cent of last year's levels, while flight bookings hit 98 per cent.
Another 400,000 students are to start school on Tuesday, and the final 520,000 on September 7.
Alex Azar says China's ruling Communist Party had the chance to warn the world and work with the world on battling the virus.
Out of the six imported cases - three were reported in Guangdong province, two in Shandong Province and one in Fujian Province. This brings the total number of imported cases to 2,004.
Twenty-seven new cases were reported in the last 22 hours, Beijing city spokesman Xu Hejian said, adding that strict measures have been implemented to stem the spread of the deadly virus.
The Beijing Municipal Health Commission on Monday said that the city reported 36 new confirmed domestically-transmitted COVID-19 cases and six new asymptomatic cases.
Out of 49 confirmed cases, 36 were reported on Monday in Beijing, traced to a wholesale market that supplies much of the city's meat and vegetables.
The officials of the China's National Health Commission (NHC) said that 57 new confirmed COVID-19 infections, including 38 domestically transmitted, were reported on Saturday.
The majority of China's cases in recent months were overseas nationals tested as they returned home, with the domestic outbreak brought largely under control after the disease first emerged in Wuhan.
As of June 10, the overall confirmed cases on the mainland reached 83,057, including 62 patients who were still being treated, with no one in severe condition.
Three imported cases were reported on Monday, including two in Guangdong province and one in Sichuan province, the National Health Commission said in its daily report on Tuesday.