The authors found that a resurgence could happen even after especially arduous periods of distancing, such as a 20-week period of social distancing. “The social distancing is so effective that virtually no population immunity is built.”

Instead, the authors argue interventions need to be made multiple times over a period of time, called “intermittent distancing,” at intervals that depend upon the state of the health care infrastructure at any moment in time, meaning, how much load it can absorb of critical care cases of the disease.

“Intermittent social distancing can maintain critical care demand within current thresholds,” they advise.

The authors suggest a threshold to be maintained is no more than 37.5 cases of the disease per 10,000 adult people in the population. That should be the “on” switch to re-commence social distancing, they argue. That threshold, they estimate, would keep the number of patients needing critical care at 0.89 persons for every 10,000 people in the population, which should be adequate to not overwhelm the health care system.