In the 1950s a batch of polio vaccine in the US was made badly, resulting in 10 deaths and the permanent paralysis of 164 people. Paul Offit, a paediatrician in Philadelphia, says the disaster did not turn people away from vaccines. He believes that current vaccine hesitancy needs to be tackled online - where fake news spreads quickly.

The German state of Brandenburg wants to make pre-school vaccinations compulsory - like neighbouring France and Italy - because immunisation rates there dropped to 73%. But some doctors believe busy parents can instead be gently persuaded to take up vaccines.

Perhaps this is where psychological research can play a role. Sander van der Linden, Director of the Cambridge Social Decision Making Lab in the UK, is working on an online game which "inoculates" people against fake news - by showing them how they can be manipulated online. He says the effects last about 6 weeks - so a "booster" may be necessary.

Head of the Vaccine Confidence Project Heidi Larson applauds 18 year old American Ethan Lindenberger who decided to get vaccinated despite his own mother's anti-vax views which he says she got from reading church and internet anti-vaccination groups rather than from the medical profession.

Producer: Paula McGrath

Picture: A vial of measles, mumps and rubella vaccine and an information sheet, Boston Children's Hospital in Boston, Massachusetts February 26, 2015. Credit: Reuters / Brian Snyder / File Photo