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Target R and Wait for the Vaccine

Opening up the economy means allowing more human interaction and hence greater potential for new #COVID19 infections. Two numbers matter for deciding whether this can be done safely any time soon.

CAMBRIDGE – Many countries are now under lockdown to lower the growth rate of COVID-19 cases and deaths. Given the astronomical costs of such efforts to “flatten the curve” of COVID-19 infections, policymakers are under growing pressure to “reopen the economy.” But how can they do so safely?

Given that it takes an average of 5.2 days between infection and the onset of symptoms, and 13 days from onset to death, if the lockdown would bring new infections to a halt, the number of new cases and deaths should drop to zero within three weeks. By this standard, the actual process has been amazingly slow. Italy, for example, imposed a severe lockdown on March 9, a day when authorities there confirmed 1,797 new cases and 97 new deaths. On April 18, the numbers were 3,491 and 482, respectively. Italians are dying at a rate four times higher than they were before the lockdown.

And yet some, including US President Donald Trump, believe it is time to relax the restrictions. If the epidemic curve is an inverted U and we have seen a peak, the worst is behind us, right?