LESS THAN a year after covid-19 spread across the world, scientists have produced several vaccines that may offer high immunity. But mass inoculation is months away. Until then people must contain the virus by wearing masks, travelling less and limiting contact with other households.
Politicians who thought their citizens would stop socialising of their own accord have been disappointed. America’s daily deaths are near record highs as the virus runs amok. Europe’s cases surged in October, causing 11 governments to reimpose national stay-at-home orders. They hope these lockdowns will reduce infections to manageable levels for Christmas. But after a grim spring, they must worry that people will be less compliant this time around.
Google’s smartphone data confirm that Europe’s latest restrictions have had less impact on daily life. In March the average number of trips—to places such as supermarkets, restaurants, transport hubs and offices—fell to 35% of the level in January. After rebounding to 83% by the time of the latest lockdowns, mobility has now dropped only to 68%. This smaller effect could be caused both by more flexible rules and less enthusiasm for obeying them.
Yet these less stringent lockdowns are still working. The London School of Hygiene and Tropical Medicine’s estimates of R—the average number of new people who catch the virus from each infected person—are dropping. In European countries that enacted second lockdowns, R fell from an average of 1.1 in the week before the new restrictions to 0.9 in the week after. That small change makes a big difference. Over four weeks, it would mean new infections falling by 21%, rather than rising by 36%.
For 334 local authorities in England and Wales (akin to America’s counties), we have also calculated which aspects of lockdowns matter most. We combined estimates of R from Imperial College London with travel records from Teralytics, a Swiss technology firm, and Google’s smartphone data. Then we used mediation analysis, a statistical technique, to disentangle the effects of different types of mobility.
We found two ways that lockdowns suppress R. First, reducing trips to work helps, as do fewer outings to restaurants, bars and shops, though the effect of those leisure settings may vary a lot. (Usage of parks or public transport had no impact, perhaps because visitors are outside or wearing masks.) Second, lockdowns deter people from travelling to other local authorities. This is probably the most important factor in decreasing R overall.
This is all good news. Looser lockdowns cost less than total closures. And when governments reopen businesses, they can mitigate extra mingling among customers by urging them to stay in their local areas, for now. That is the best way to get the virus under control before Christmas. ■
Sources: Covid19-projections.com; Google; Teralytics; Blavatnik School of Government, University of Oxford; Swapnil Mishra et al., Imperial College London; Sam Abbott et al., London School of Hygiene and Tropical Medicine
This article appeared in the Graphic detail section of the print edition under the headline “Second act”