(CNN) People in high-income countries have the lowest confidence in vaccines, with about 20% of those in Europe either disagreeing or being unsure of whether vaccines are safe, according to a new global survey.

The Wellcome Trust, a UK medical research charity, asked more than 140,000 people ages 15 and older in more than 140 countries how they think and feel about health and science.

Globally, about 8 in 10 people (79%) agreed that vaccines are safe, and 9 in 10 worldwide say their children have been vaccinated, but Wellcome said there were pockets where trust in vaccines was of concern.

"Vaccines, for example, are one of our most powerful public health tools, and we need people to have confidence in them if they are to be most effective," said Jeremy Farrar, director of the Wellcome Trust.

"No matter how great your idea, how exciting your new treatment or how robust your science, it must be accepted by the people who stand to benefit from it," he added.

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