South Korea brought in another 835,000 doses of AstraZeneca's COVID-19 vaccines, enough for 417,500 people on Thursday amid concerns over a tight vaccine supply.

The vaccines developed by the British-Swedish pharmaceutical giant and Oxford University are shipped in under the World Health Organization's global vaccine COVAX Facility project.

So far, AstraZeneca vaccines, under COVAX, for 1.26 million people have already been brought in, with another shipment of the products for 835,000 people slated for June.

A series of mishaps in securing COVID-19 vaccines as scheduled has spawned concerns that the country's nationwide inoculation scheme may be delayed, which in turn may put its goal to create herd immunity by November in jeopardy.

The shipment also comes as health authorities have been speeding up the vaccine rollout that kicked off in late February, by giving out second shots.

The bottles that recently arrived will be used to give the second shots for the elderly population aged over 75, as well as for the first shots of elders aged between 65 and 74, those suffering from chronic respiratory diseases and those working at nursery schools.

South Korea has secured enough COVID-19 vaccines to inoculate 99 million people under COVAX and separate contracts with five foreign drug firms, including AstraZeneca.

As of Wednesday, a total of 3.71 million people, or 7.2 percent of the population, have been given COVID-19 vaccine shots.

AstraZeneca's vaccine has been administered to 2.03 million people, while 1.67 million people have received that of Pfizer Inc.

A total of 82,890 people have received two doses. (Yonhap)