Gates, in Berlin for a donor conference of the GAVI alliance bringing vaccines to poor countries, said the risk of a worldwide pandemic meant it was reckless not to act now.
"A more difficult pathogen (than Ebola) could come along, a form of flu, a form of SARS or some type of virus that we haven't seen before," he said in an AFP interview.
"We don't know it will happen but it's a high enough chance that one of the lessons of Ebola should be to ask ourselves: are we as ready for that as we should be? A good comparison is that we prepare ourselves for war -- we have planes and training and we practise."
Gates, ranked by Forbes magazine as the world's richest man with a net worth of some USD 80 billion, said the Bill and Melinda Gates Foundation distributes about USD 4 billion each year to help the world's neediest.
It is also a major contributor to the GAVI alliance, which on Tuesday drew pledges of USD 7.5 billion to help immunise 300 million more children in developing countries over the next five years.
However he said he was "concerned" about an anti-vaccination trend in the West, due to exaggerated fears of risks associated with the jabs, that was leading to dangerous outbreaks.
"Our focus is on the poor children where you have millions that die of vaccine-preventable disease. It's unfortunate that you're not getting 100-per cent coverage in the rich countries," he said.
"They're choosing to potentially infect somebody who can't protect themselves," he said, noting the renewed spread of illnesses such as measles and pertussis (whooping cough).
The Microsoft co-founder said that technology was a crucial asset in his foundation's field work, seen most recently in a drive against polio.
Gates said he was proud to have inspired fellow American billionaires such as Warren Buffett to devote a big slice of their wealth to charity and was working to spread the message in Europe, India and China.
