Russia claimed Tuesday it has developed the world's first vaccine offering "sustainable immunity" against the coronavirus, despite mounting scepticism about its effectiveness as fears grow over a second wave of infections across the globe.

President Vladimir Putin said the vaccine was safe and that one of his own daughters had received the inoculation, dubbed "Sputnik" after the pioneering 1950s Soviet satellite. 

"I know that it is quite effective, that it gives sustainable immunity," Putin said of the vaccine developed by the Gamaleya research institute in coordination with Moscow's defence ministry. 

Russia's health ministry said though clinical trials were not yet complete and final stage testing involving more than 2,000 people was to start only on Wednesday.

Western scientists have previously raised concerns about the speed of development of Russian vaccines, suggesting that researchers might be cutting corners.

The World Health Organization's spokesman in Geneva Tarik Jasarevic said it was in "close contact" with Russian health authorities but that it was too soon for any WHO stamp of approval.

"Pre-qualification of any vaccine includes the rigorous review and assessment of all the required safety and efficacy data," he said.

In Berlin, a spokesman for the German health ministry told newspaper group RND that "there is no known data on the quality, efficacy and safety of the Russian vaccine," adding that "patient safety is of the highest priority."

- Over a billion doses -
Russia hopes to begin production in September and start vaccinating medical staff immediately afterwards. 

Kirill Dmitriev, the head of the Russian sovereign wealth fund that helped develop the vaccine, said the doubts about the vaccines were part of "coordinated and carefully orchestrated media attacks" designed to "discredit" the country. 

He said that 20 foreign countries have pre-ordered over a billion doses.  

The race for a vaccine is heating up as nations across the globe brace for new outbreaks of the disease -- even as they try to restart economies battered by months of lockdown. 

Indonesia said Tuesday it would launch a Phase 3 human trial of a vaccine candidate from China's Sinovac Biotech.

Phase 3 refers to trials involving large numbers of human test subjects and is usually the last step before regulatory approval.

Sinovac's vaccine, dubbed CoronaVac, is already being tested on 9,000 Brazilian health workers.

The WHO says that 165 candidate vaccines are being worked on around the world, with six reaching Phase 3.

But emergencies director Michael Ryan warned that finding a vaccine would not automatically spell the end for COVID-19. 

"We have perfectly effective polio and measles vaccines, and we still struggle to eradicate or eliminate those diseases. You've got to be able to deliver that vaccine to a population that want and demand to have that vaccine," he said.

- Second waves 'inevitable' -
According to an AFP tally, the number of confirmed infections worldwide since the virus first emerged in China late last year has passed 20.1 million, with almost 737,000 deaths, with that number expected to surpass 750,000 within days.

In the United States, the world's worst hit nation, the death toll had risen to 164,480 as of Tuesday evening, with 1,110 more fatalities in the past 24 hours, according to the tracker at Johns Hopkins University. It said the total caseload of infections now stands at 5.14 million.

At the other end of the spectrum, New Zealand on Tuesday broke a more than 100-day streak without locally transmitted coronavirus infections.

"We have all worked incredibly hard to prevent this scenario," Prime Minister Jacinda Ardern said, but "we have also planned and prepared for it."

So far, New Zealand has reported just 22 deaths from coronavirus, although authorities repeatedly warned a second wave was "inevitable".

The remote Himalayan kingdom of Bhutan on Tuesday announced its first coronavirus lockdown after having been largely shielded from the disease for months.

And in Europe, the European Union's ECDC health agency urged countries to reinstate some controls as new cases began to pick up again.

France has reimposed mask-wearing in certain crowded areas and tourist hotspots of the capital Paris.

Prime Minister Jean Castex said he would ask local authorities "to extend as far as possible the obligation to wear masks in public spaces".

Castex added that unless the French public acted individually and collectively, "we expose ourselves to a high risk of epidemic resumption that will be difficult to control."

Several French towns and cities have already tightened mask rules, as have parts of Belgium, the Netherlands, and Romania.

In Spain, authorities have ordered nationwide mask-wearing in public places and some regions have returned to lockdown.

"It's a critical moment, we are right at a point where things can get better or worse," Salvador Macip, an expert in health sciences at Catalonia's Open University, told AFP.

"We have to pull out all the stops to curb outbreaks before they become more serious."

Spain has added an average of almost 5,000 new cases per day over the past week -- more than France, Britain, Germany and Italy combined.

Trump announces sixth vaccine contract

President Donald Trump on Tuesday announced a $1.5 billion contract with US biotech company Moderna for 100 million doses of an eventual coronavirus vaccine, the sixth such deal reached since May.

"I'm pleased to announce that we have reached an agreement with Moderna to manufacture and deliver 100 million doses of their coronavirus vaccine candidate," Trump said at a White House news conference. "The federal government will own these vaccine doses, we're buying them."

"We're on track to rapidly produce 100 million doses as soon as the vaccine is approved, and up to 500 million shortly thereafter, so we'll have 600 million doses," he added.

Moderna, in partnership with the US National Institutes of Health (NIH), is conducting Phase 3 clinical trials of a vaccine candidate and manufacturing of vaccine doses will take place while the trials are underway.

The vaccine, called mRNA-1273, is being co-developed by Moderna and the NIH's National Institute of Allergy and Infectious Diseases (NIAID), which is led by Dr Anthony Fauci.

Fauci has said researchers are unlikely to know the efficacy of the vaccine before the end of the year at the earliest. But Trump has said he hopes to have a vaccine before the November 3 presidential election.

The latest contract brings the US government's total commitments to Moderna to $2.48 billion.

The company, founded less than 10 years ago, has not previously developed a vaccine of any kind but preliminary results of the company's experimental COVID-19 vaccine have reportedly produced promising results.

The Trump administration has allocated a total of at least $10.9 billion for the development and manufacturing of a coronavirus vaccine.

It has already ordered 100 million vaccine doses from Johnson & Johnson, Novavax, Pfizer and Sanofi and 300 million from AstraZeneca.