More than 14 million Shanghai residents have conducted COVID-19 antigen self-testing since Saturday, which will continue on Sunday to quickly detect positive cases.Shanghai has launched a new round of screening by both nucleic acid testing in key areas and antigen self-testing for non-key area residents over the weekend."\\;The blending of PCR and antigen self-testing can enhance the screening efficiency and find hidden infections in time,"\\; said Wu Qianyu, an official with the Shanghai Health Commission.