Depending on big data of epidemic prevention provided by local public security departments, QR code cards are made for the elderly, students and other special groups such as the disabled without smart phones.

"To provide better user experience, we launched the trial operation in one community in early March," he said. "During the one-month operation, we upgraded and solved several problems raised by the users."

"In the past two years, I often felt embarrassed when I visited a public venue because I didn't know how to use a smart phone," said Gao Changyong, 73, a retired teacher. "I had to wait for the staff to write down my information, which took more time than scanning code."

"Sometimes we seniors had to queue up outside, which was insufferable, especially in the extremely cold winter," he said. "Therefore, I often asked my children to send me daily supplies to avoid going out."

"When the community worker told me the new method, I was really happy and immediately submitted my application," he said. "I received the card just a few days later, which had made my life more convenient and efficient."