Mobility restrictions, social distancing help stem COVID-19 tide

Restricting mobility seems to be an effective approach to control the novel coronavirus disease (COVID-19) pandemic and leads to declining transmission, a recent analysis has shown. 

Data regarding COVID-19 deaths were sourced from the World Health Organization (WHO) and the European Centres for Disease Control, while data for mobility were obtained from Apple and Google, which collected movement information from mapping apps. Fifty-two countries had sufficient epidemiological and mobility data and were included in the analysis.

Overall, the median mobility across all countries was lowest on 11 March 2020, during which mobility was 63-percent lower than baseline. In turn, the virus’ effective reproduction number dropped sharply, according to statistical models. This was also true for the estimated reproduction number for deaths.

Notably, by the second half of May 2020, there was a slight decoupling of mobility and transmissibility. As movement started to gradually increase, so did transmissibility, but at a slower pace than expected.

The researchers then sought to determine mobility thresholds that could keep the virus’ reproduction number below 1.0. They found that, at least in the UK, an initial 43-percent mobility reduction would be necessary, but after considering other social distancing behaviours, the threshold could be as low as 18 percent. These values varied largely for the different countries assessed.

“We found strong evidence that the relationship between mobility and transmissibility changed over time, typically, a dampening indicating that smaller reductions in mobility can result in epidemic control likely due to other social distancing behaviours,” the researchers said.

“As many countries are re-imposing social-distancing policies, our analysis illustrates that sustainable relaxation of population-wide social-distancing measures should be undertaken very carefully and replaced with equally effective control measures, such as thorough contact-tracing,” they added.