I. The Early Warning and Preparation phase of a pandemic economy starts at the time when WHO issues an early warning for virus outbreaks, and governments begin to prepare accordingly, mainly including restrictions on travel to and from known epidemic centers.
II. During the Emergency Response phase, the virus infections emerge in different locations, with even community outbreaks. Countries adopt and implement non-pharmaceutical interventions (NPIs), including closures of schools and workplaces, quarantines and social distancing, etc. Societal level human mobility declines or even plummets. In a PET graph, the starting time (Point A) is the day before people's mobility shows a clear downward trend.
III. In the Recovery phase, epidemic growth decelerates, transmissibility declines progressively, and human mobility gradually rises. The starting time (Point C) is characterized by a tipping point when the recovered individuals start to outnumber new cases in a consistent manner (i.e., a minimum of three consecutive days), which means that more capacity of the health system is released.
IV. In the Trough phase, the declining trend of mobility starts to slow down and turns into a prolonged period of fluctuating around a low level, limiting the spread of the virus from people to people. The starting time (Point B) is the end of the descending trend when people's mobility reaches a local minimum.
V. The Vaccination phase starts when WHO announces the success of the development of a new COVID-19 vaccine (Point D). Mass production is made possible, followed by equitable and speedy deployment worldwide, then the economy decouples from the pandemic.