Less than six per cent of the French will have contracted the coronavirus by the time the country starts lifting lockdown next month, according to a major new study, which warned of a high risk of a “second wave” unless drastic social distancing is maintained.

The Pasteur Institute findings confirmed the “massive impact” of nationwide confinement in place since March 17 in France and which it estimates means that only 3.7 million people - some 5.7 per cent of the population - will have been infected by May 11 when lockdown is gradually lifted.

In their “snapshot” of France published by national research institute Inserm, experts estimated the rate of infection per person with the virus had fallen from 3.3 before lockdown to 0.5 today - an 84 per cent drop.

While highly effective in preventing the collapse of the health system in a country that saw deaths from the virus surpass 20,000 this week, confinement now poses a major problem, it warned.

“Our results strongly suggest that without a vaccine, group immunity will be insufficient alone to avoid a second wave at the end of lockdown. Efficient control measures must be maintained beyond May 11, it said.