Microsoft billionaire Bill Gates says he's ready to "waste" billions of dollars on vaccines for COVID-19 that don't work, just to make sure the world gets one that does. 

COVID-19 has killed tens of thousands of people in the past couple of months, at an accelerating rate, and as yet there's no known cure or vaccine for it. 

Scientists around the world are racing to find them, and have come up with a few potential candidates - but under normal processes, it could be months or even years before they're ready.

Gates doesn't want to waste any time. In a new interview with US comedy/news programme The Daily Show, the former richest man in the world said his charitable foundation is starting to build vaccine factories now for seven promising candidates, even though there's no undeniable proof yet any of them work.

"Even though we'll end up picking at most two of them, we're going to fund factories for all seven just so we don't waste time in serially saying 'OK, which vaccine works?' and then building the factory," he told host Trevor Noah, in a clip released ahead of the episode's airing in the US.

"It'll be a few billion dollars we'll waste on manufacturing for the constructs that don't get picked because something else is better. But a few billion in this situation we're in, where there's trillions of dollars - a thousand times more - trillions of dollars being lost economically, it is worth it."

• 82 new cases bringing total to 950
• US accused of 'piracy' for taking face masks bound for Germany
• China hoards world’s masks, sells them back; CCP virus is right name: poll; hospital fakes recovery
• Update – 3rd April, 2020

Gates, with his wife Melinda, runs the Bill & Melinda Gates Foundation. Since its formation in the 1990s the foundation has spent billions on fighting diseases like malaria, tuberculosis and HIV, with help from other billionaires like Warren Buffett. 

Gates said governments will take a few months to begin manufacturing and funding for vaccines underway, but because he's got funds to burn, he's able to get started right away.

In the meantime, he said there would be a "lot of unusual measures" needed to fight the spread of the virus before the world can be vaccinated.

"Seven billion people, that's a tall order, but it is where we need to get to." 

Gates earlier this week called on the US to implement a nationwide shutdown, like New Zealand has. 

Two likely candidates for Gates' seven vaccines were announced just this week. On Friday morning (NZ time), scientists at the University of Pittsburgh School of Medicine said they'd developed a Band-Aid style patch which triggered an antibody response in mice that could hold off the disease for probably a year.

And later that afternoon, researchers in Australia said they'd come up with a treatment, based on previous effort to make a vaccine against SARS, which could potentially work.

"As soon as the genomic sequence of COVID-19 became available in January, we immediately used this, combined with our previous experience in developing a SARS coronavirus vaccine, to characterise the key viral attachment molecule called the spike protein," said Nikolai Petrovsky of Flinders University in Adelaide.

"We used computer models of the spike protein and its human receptor, ACE2, to identify how the virus was infecting human cells, and then were able to design a vaccine to block this process."

It's currently undergoing animal testing, and human trials are hoped to begin within a few months.