Tianjin Municipality has begun its second citywide round of nucleic acid testing after recently reporting a COVID-19 flare-up. The flare-up was detected in Jinnan District, where two people tested positive on January 8. Following the resurgence, the port city launched its first citywide round of mass testing at 7 a.m. on Sunday. A total of 11,912,280 people were sampled in the testing drive. Municipal officials have also offered door-to-door nucleic acid sampling services for the elderly.