The study, conducted by Gallup and funded by global health charity The Wellcome Trust, found one-in-three French people think vaccines are unsafe - the highest rate in the world - and almost 20 per cent believe they are not effective.

Researchers say the picture in France is the result of factors that have undermined public confidence - not only in vaccines, but also in science more broadly, in the government and in the pharmaceutical industry.

This "cumulative breakdown" of trust in turn has led some French people to delay or refuse vaccines, said Heidi Larson, director of the vaccine confidence project at the London School of Hygiene and Tropical Medicine.

The World Health Organisation said making vaccines mandatory is one of the best ways to boost immunisation rates.

France decided last year to up the number of compulsory vaccines to 11 from three for babies under two years old.

David Zumino, a 47-year-old intellectual property consultant and father of three children, including a one-year-old, says that rule change means he and his wife are again "constantly trying to assess whether vaccination is really worth it".

"Of course, we understand there are medical benefits for the children," he told Reuters as he visited the Paris pharmacy where Grime works.

"But I can't help thinking that there is a huge pharma lobby operation to convince the public there is a threat that needs to be addressed. And that sounds suspicious."

David Loew, an executive at the drug- and vaccine-maker Sanofi Pasteur, puts French scepticism down to misinformation.

"There have been in the past years a lot of theories connecting vaccines to various health issues. There is also fake news circulating on social media which poses a real problem," he told reporters last week.

Australian Associated Press