American billionaire, Bill Gates, says over 80% of the global population would have to take a vaccine for the coronavirus disease (COVID-19) for it to work as a solution to the pandemic.

Since the novel disease was detected in China in December 2019, over 6.7 million people have been infected across the world, with nearly 400,000 dead.

Over 3.2 million people have also recovered from infection, but that's due mostly to medical treatment used to aid immune system of patients to fight the disease.

Many governments and organisations around the world have for months been working on vaccines to significantly put an end to the spread of the disease, but there is no definite timeline on when that goal will be achieved.

Gates, the founder of Microsoft, has been the target of many conspiracy theories alleging that he has sinister motives behind pushing for vaccines for coronavirus, and other diseases.

While some conspiracy theorists allege that he wants to use the pretext of the vaccine to inject people with microchips to track them, some others say it's part of his evil plan to depopulate the world.

Others have suggested that the virus was deliberately unleashed on the world so that people can make money from selling a cure.

Some of the theories have circulated in Nigeria where 11,516 coronavirus cases have been recorded, killing 323 people.

The Bill and Melinda Gates Foundation, run by Bill (left) and his wife, Melinda (right), is reported to be the largest private foundation in the world [Ted S. Warren/AP]
The Bill and Melinda Gates Foundation, run by Bill (left) and his wife, Melinda (right), is reported to be the largest private foundation in the world [Ted S. Warren/AP]
Ted S. Warren / AP

Gates said the theories are harmful to the efforts to save the world from the coronavirus pandemic during an interview with Radio 4 on Thursday, June 4, 2020, according to a report by the Daily Mail.

The billionaire said such outrageous theories could derail efforts to get a majority of the world to take the vaccines and put an end to the coronavirus disease.

He said, "It is troubling that in times like that, and accelerated by digital tools, there is so much craziness.

"Eventually when we have the vaccine, we will want to develop the herd immunity to have over 80 per cent of the population taken.

"If they have heard that it is a plot, or vaccines in general are bad, and we don't have people willing to take the vaccine, then that will let the disease continue to kill people.

"So it is a bit worrying that there is some of that crazy stuff."

The Daily Mail reports that the Bill and Melinda Gates Foundation, which Gates runs with his wife, has donated more than $250 million to the search for a coronavirus vaccine.

Gates said he's surprised to be a target of conspiracy theorists because all he does is to give money away to relevant institutions to find solutions to health problems.

"We just write cheques to pharma companies (and) we happen to have a lot of the smart pharmaceutical expertise in our foundation, and are considered a fair broker between governments and the companies to help pick the best approach," he said.

A coronavirus vaccine, developed in the United Kingdom, could be ready for deployment in September if clinical trials prove it works [Reuters]
A coronavirus vaccine, developed in the United Kingdom, could be ready for deployment in September if clinical trials prove it works [Reuters]

The Brazilian Health Regulatory Agency (ANVISA) announced earlier this week that it had approved the inclusion of Brazil in the clinical trials of a vaccine conducted by Oxford University and supported by AstraZeneca.

Clinical trials of the vaccine, named AZD1222, are also taking place in the United Kingdom, and the United States, which has been worst-hit with nearly 2 million infections.

The global supply of the vaccine has been doubled to 2 billion after a deal including $750 million from the Bill and Melinda Gates Foundation.

According to the BBC, 300 million of the potential vaccines are already pledged to the US, and 100 million to the UK.

The first doses could be ready by September if clinical trials prove that AZD1222 works.