Before revision:  The fraction of immunized people reached a plateau below 1\% throughout France (3\% in Paris) by late April 2020 (95\% c.l.), suggesting a lack of herd immunity and that a second wave of the pandemic is possible during the partial lifting of the national lockdown. After the partial lifting of the lockdown, if R_0 is as high as 1.5, then a second wave will lead to 60 thousand deaths by mid-July and over a million by October , while if R_0 is 1.2 or lower, the pandemic is delayed with deaths rising as late as August, allowing for timely governmental response .
After revision:  The fraction of immunized people reached a plateau below 1\% throughout France (3\% in Paris) by late April 2020 (95\% c.l.), suggesting a lack of herd immunity . The widespread availability of face masks on 11 May, when the lockdown was partially lifted, should keep R_0 below unity if at least 46\% of the population wear them outside their home. Otherwise, without enhanced other social distancing, a second wave will lead to 60 thousand deaths by mid-July and over a million by October , while if R_0 is 1.2 or lower, the pandemic is delayed with deaths rising as late as August, allowing for timely governmental response .