Bill Gates has compared tackling the coronavirus pandemic to fighting a world war.

In a memo on his website, Gates Notes, the co-founder of Microsoft wrote that the whole world is in a fight against the virus.

“The coronavirus pandemic pits all of humanity against the virus. The damage to health, wealth, and well-being has already been enormous,” Mr Gates said.

“This is like a world war, except in this case, we’re all on the same side,” he added.

Mr Gates wrote that the coronavirus pandemic will be the defining moment for anybody that lives through it.

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“Melinda and I grew up learning that World War II was the defining moment of our parents’ generation,” he wrote.

“In a similar way, the Covid-19 pandemic-the first modern pandemic-will define this era. No one who lives through pandemic will ever forget it.”

His philanthropic group that he founded with his wife Melinda, The Bill & Melinda Gates Foundation, has donated over $250 million to help fight the outbreak, and Mr Gates has spoken publicly multiple times about the need to develop a vaccine.

Writing on his website, he said that at this point no one knows how long it will take to create a vaccine that can be safely used.

“I am often asked when large-scale vaccination will start. Like America’s top public health officials, I say that it is likely to be 18 months, even though it could be as short as nine months or closer to two years,” he said.

“A key piece will be the length of the phase three trial, which is where the full safety and efficacy are determined.”

Mr Gates elaborated on his vaccine hopes on, The Late Show with Stephen Colbert, on Thursday, and said that “we’ll understand by this summer,” how long it will take for a working vaccine.

“We’ll see, because they are going into humans now, we’ll see if they get this strong antibody response and then we have to do product safety testing and get the manufacturing going,” the 64-year-old added.

Speaking to the Financial Times, earlier in the month, Mr Gates warned that a viral pandemic, similar to the coronavirus outbreak, could happen every 20 years.

“So now people realise, ‘OK, there really is a meaningful probability every 20 years or so with lots of world travel that one of these [viruses] will come along,’” he said.

“And so the citizens expect the government to make it a priority.”