London(CNN) Anti-vaccination "fake news" being spread on social media is fueling a rise in measles cases and a decline in vaccination uptake, the head of England's National Health Service (NHS) has warned.
Simon Stevens said "vaccination deniers" are gaining traction through their use of social media platforms including Instagram, WhatsApp and YouTube.
"Across the world, two to three million lives are saved each year by vaccination," Stevens said at a health summit on Friday. "But as part of the fake news movement, actually the vaccination deniers are getting some traction.
"Last year, for example, we saw more than triple the number of measles cases across England than we had seen the year before despite the fact that clearly, vaccination works," he added.
Anti-vaccination groups frequently use social media platforms to spread conspiracy theories or misinformation about vaccine use, despite the fact that such theories have been conclusively debunked by the medical community.
Stevens said discussions within the health body have focused on how to stem the spread of anti-vaccination ideas on Instagram and YouTube, and referred to a parent at his daughter's primary school who had used WhatsApp to express concern about children's immune systems being "loaded up" with vaccines.
This week, YouTube removed commercials from videos that promote anti-vaccination ideas.
Stevens said that the vast majority of people who understand the benefits of vaccinations must "win the public argument" in order to reverse the trends.
"We are not being helped on this front by the fact that although nine in 10 parents support vaccination, half of them say they have seen fake messages about vaccination on social media," he added.
In January, the Royal Society for Public Health (RSPH) warned social media is helping to spread "misleading and dangerous information" about vaccines. Their study said social media is a "breeding ground for misleading information and negative messaging around vaccination."
Britain has better vaccination uptake rates than much of Europe, but has not been immune to the wave of misinformation surrounding vaccines that has swept through the continent.
The proportion of children being immunized against measles, mumps and rubella (MMR) in England has fallen for four consecutive years, NHS figures show.
"In 2017, Britain was declared free of endemic measles, with just 259 lab-confirmed cases. But last year saw 913 confirmed cases of this potentially fatal yet entirely preventable disease -- a three-fold increase," Stevens said. "This has been exacerbated by myths propagated largely online."
Anti-government control sentiment "continues to be a thread in the anti-vaccine movement -- particularly in this era of mistrust in government," Professor Heidi Larson, director of the Vaccine Confidence Project at the London School of Hygiene and Tropical Medicine, told CNN last month.
Vaccine hesitancy is one of the biggest threats to global health in 2019, according to the World Health Organization.
"Vaccination is one of the most cost-effective ways of avoiding disease -- it currently prevents 2-3 million deaths a year, and a further 1.5 million could be avoided if global coverage of vaccinations improved," WHO said.
A spokesperson for Facebook, which owns WhatsApp and Instagram, said: "We don't want misleading content on Facebook and have made significant investments in recent years to stop misinformation from spreading and to promote high-quality journalism and news literacy.
"That said, we always try to strike a balance between allowing free speech and keeping people safe -- which is why we don't prevent people from saying something that is factually incorrect, particularly if they aren't doing so intentionally."
CNN has also contacted Google, which owns YouTube, for comment.