The sweeping shutdowns across the world appear to have absorbed what may only be the first wave of coronavirus disease (Covid-19) infections, according to officials from the World Health Organization (WHO) and findings by researchers in France – one of the countries hardest hit by the pandemic.

The assessment is based on the number of people who appear to have contracted and recovered from the disease – the only way to develop an immunity till the time a vaccine is developed – which, according to WHO director-general Tedros Adhanom Ghebreyesus, “was not more than 2-3%”.

“Early data suggests that a relatively small percentage of the populations may have been infected, even in heavily affected areas,” Tedros said at a briefing in Geneva on Monday, after warning that the “the worst is yet ahead of us”. The estimates were based on detection of antibodies in the regions where blood tests have been carried out.

The findings are backed by a research uploaded to the French open access journal HAL. “By 11 May, when interventions are scheduled to be eased, we project 3.7 million (range: 2.3-6.7) people, 5.7% of the population, will have been infected. Population immunity appears insufficient to avoid a second wave if all control measures are released at the end of the lockdown,” the authors say in the report .

France accounts for the highest number of infections as well as fatalities after the United States, Spain and Italy. As on Tuesday, 155,383 have been infected and at least 20,000 have died in France. The country ordered a nationwide shut down on March 17 when infections were at close to 7,000 with 175 fatalities.

The researchers also add that an analysis of hospitalisations and ICU admissions suggest the lockdown had a drastic impact in France. “We find that the basic reproduction number R0 prior to the lockdown was 3.31 (95% CrI: 3.18-3.43). At the national level, the lockdown resulted in a 84% reduction in transmission with the R dropping to 0.52 (95% CrI: 0.50-0.55),” they said. R0 or R naught is the number of people infected by one person carrying the virus. A 95% Crl means there is a 95% probability that a value falls in a particular interval, also called credible interval or Crl.

“National daily ICU admissions have gone from 700 at the end of March to 220 on the 14th of April. If current trends continue, by the 11th of May, we project between 10 and 45 daily ICU admissions,” the researchers add.

This suggests France may have “flattened the curve”, a disease containment strategy that aims to reduce infections to levels that a country’s health infrastructure can manage.

With a population of 1.36 billion, this is especially hard for a country like India, which has one doctor for every 1,457 people. France, on average, has 3.2 doctors for every 1,000 people, according to World Bank data.

Globally, more signs emerged that the lockdowns that began in mid-March may have helped enough for some of these curbs to be relaxed in some areas. On Tuesday, Germany reported the smallest increase in infections – 1,323 – in a month. German chancellor Angela Merkel told a meeting of her Christian Democratic Party on Monday that easing the curbs risks sparking a new wave of infections.

In Australia, health minister Greg Hunt said the lockdown measures have led to a “sustained and consolidated” slowdown in new infections – he said the growth rate had been less than 1% for nine consecutive days – but cautioned that there would be no relaxations for at least three more weeks.

(With inputs from Bloomberg)