The co-founder of Microsoft, whose Gates Foundation is heavily involved with Gavi, The Vaccine Alliance in trying to find a coronavirus vaccination, said that those against the vaccine – the so called ‘anti-vaxxers’ – would let COVID-19 “continue to kill people”.
He told BBC Radio 4's Today programme: "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% 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.”
Commenting on the conspiracy theories surrounding Gates himself, he added: "I'm kind of surprised that some of that is focused on me.
"We are just giving money away to get there to be a tool – 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.”
Scientists at Oxford University began human trials on a potential coronavirus vaccine in April, in a study involving over 500 people.
Initial results over whether the vaccine works are expected as early as mid-June.
Business secretary Alok Sharma – who is being tested for COVID-19 after appearing unwell in the House of Commons – in May said tests being carried out at Imperial College London were “making good progress”, with clinical trials set for later this month.
The government recently announced a further £84m in funding in the race to find a vaccine.
The business secretary said: "This new money will help mass-produce the Oxford vaccine so that if current trials are successful we have dosages to start vaccinating the UK population straight away."
Pharmaceutical firm AstraZeneca has finalised a "global licensing agreement" with Oxford University with government support – meaning 30 million doses could be available by September for the most vulnerable in the UK.
Health secretary Matt Hancock has previously said that 100 million doses of a vaccine would be available for the UK under the terms of the AstraZeneca deal.