Statewide physical distancing policies work, a new modeling study finds. Deaths from Covid-19 declined and the incubation time for new cases grew.
Researchers from Harvard University and University College London found that every state in the US passed at least one physical distancing measure in March to slow the spread of the pandemic –– and it did.
Policies were so successful, physical distancing resulted in the reduction of more than 600,000 cases within just three weeks, according to the study, published Tuesday in the journal PLOS. Had there not been preventative interventions, the models suggest up to 80% of Americans would have been infected with Covid-19.
Due to these policies, the time it took to double cases increased from about four days to eight within three weeks of that statewide policy going into place.
The case growth rate declined by about 1% per day starting four days after a statewide measure was put on the books. Per week, the model suggests the policies resulted in 1,600 fewer cases by week one, and about 621,000 fewer cases by week three.
Other studies of these physical distancing policies have shown similar results, but the authors said this is the first study to show that these polices saved lives. The death rate decreased by 2% per day beginning a week after a physical distancing policy started.
Something to note: There are limits to this model. This isn’t a controlled experiment. If states made stronger physical distancing policies in response to a worsening local epidemic, the policies may not have looked as effective, the authors said. The model also can’t account for people who stayed home and avoided crowds out of concern for their own safety, rather than to follow their state policy.
"The results show the timing of government-issued orders correlated strongly with reductions in both cases and deaths. In short, these measures work, and policy makers should use them as an arrow in their quivers to get on top of local epidemics where they are not responding to containment measures,” Dr. Mark J. Siedner in a statement.
Siedner is a co-author of the study and an infectious diseases doctor at Massachusetts General Hospital and Associate Professor of Medicine at Harvard Medical School.