'"Fake news" by anti-vaxers on social media has fuelled a tripling in measles cases and is risking lives, the head of the NHS has said.
Simon Stevens said the promotion of misguided messages on Instagram and YouTube was one of the factors behind an alarming dip in vaccine coverage.
He said parents at his local school were among those circulating advice which was against all evidence about the effectiveness of vaccines.
He told a health policy summit: "One thing we are very concerned about at the moment is around vaccination in this country. Across the world two to three million lives are saved each year by vaccination."
Official figures show 913 cases of measles in England between January and October last year - compared with 259 in the whole of the previous year.
Mr Stevens said that parents who failed to get their children vaccinated were as irresponsible as if they failed to teach their children to look left and right before crossing the road.
He told the Nuffield Trust health policy summit: "As part of the ‘fake news’ movement the vaccine deniers are getting some traction.
"And so for last year for example we saw triple the number of measles cases that we had seen the year before, despite the fact that vaccination works.
"We have seen a five-year steady decline in vaccination uptake and the consequence of this is that very effective and important health interventions that we have got to continue to win the public argument about."'
Read more: Anti-vaccination fake news on social media fuels tripling in measles cases, head of NHS says