Residents register for coronavirus testing at a designated site in Qingdao, China, on Oct 14, 2020. (PHOTO / XINHUA)

QINGDAO - More than 7.5 million people had been sampled for nucleic acid testing by 9:30 am Wednesday in east China's Qingdao city, after it began a city-wide testing campaign on Monday.

More than 4.06 million of the collected samples have been tested so far and no new positive samples have been detected, with the exception of the cases that had already been reported, the municipal health commission said.

More than 4.06 million of the collected samples have been tested so far and no new positive samples have been detected, with the exception of the cases that had already been reported, Qingdao's municipal health commission said

Qingdao has a population of more than 11 million. The city has vowed to complete city-wide nucleic acid testing within five days starting from Monday.

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Five cities in Shandong, including Zibo, Yantai and Rizhao, have joined hands with Qingdao to help conduct nucleic acid sampling and testing, and more than 1,200 people have been dispatched to the city to assist in testing, Chen Wansheng, an official with the municipal government, said Wednesday.

In total, more than 10,000 medics and 20,000 volunteers have joined in to facilitate the testing.

"The National Health Commission has urgently allocated 9,000 milliliters of convalescent plasma from recovered COVID-19 cases for the treatment of severe patients in Qingdao," Chen said.

A mixed testing approach has been adopted to improve efficiency, according to Zhang Huaqiang, an official with the municipal health commission.

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"If a 10-in-1 sample is positive, we will inform the 10 people to undergo separate isolation and testings to further identify carrier of the positive sample," said Zhang.

Qingdao has reported 12 new COVID-19 cases since the virus re-emerged in the city over the weekend, the municipal health commission said.