Passengers pass security checkpoint at Terminal 2 building of the Shanghai Pudong International Airport in east China's Shanghai, Nov. 24, 2020. (Photo: Xinhua)

China has tweaked COVID-19 prevention playbook to shorten collective quarantine time of close contacts and intl arrivals to 7 days. It also unified the standard of classifying high-, medium-risk areas, based on if new cases emerge in the past 7 days.