Several social networks including Pinterest and YouTube have detailed measures they are taking in response to pressure to combat disinformation on vaccines, which they have been accused of enabling.
Pinterest confirmed to AFP Monday it changed its policy last year with regards to anti-vaccine content, a development first disclosed last week by the Wall Street Journal.
The company said it had started blocking certain searches related to vaccinations and cancer cures last year because results were leading to harmful misinformation.
"We want Pinterest to be an inspiring place for people, and there's nothing inspiring about misinformation," a spokesperson said.
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"That's why we continue to work on new ways of keeping misleading content off our platform and out of our recommendations engine."
Besides blocking search results, the site has also barred accounts and removed "pins" that violate its rules on medical disinformation, but the spokesperson was unable to give specific numbers.
YouTube announced Friday it was removing ads on anti-vaccine videos, thus eliminating a key way such videos make money.
"We have strict policies that govern what videos we allow ads to appear on, and videos that promote anti-vaccination content have been and remain a violation of our longstanding harmful or dangerous advertising policy," YouTube said in a statement.
Buzzfeed had drawn attention to instances in which YouTube's automated recommendations system had allowed some anti-vaccine videos to slip through.
Pressure is growing on social networks in the United States and elsewhere to take action in the face of criticism that they have enabled the development of an anti-vaccine movement.
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Several outbreaks of measles in the US have sickened 159 people since the start of the year, including 65 in Clark County, Washington state. Most of the cases involved non-vaccinated children.
According to US health authorities, the percentage of children aged two or over who have not been vaccinated has gone from 0.9 per cent of children born in 2011, to 1.3 per cent of those born in 2015.
In 2017-2018, the number of requests for vaccination exemptions rose for the third school year in a row in the United States.
Democratic lawmaker Adam Schiff wrote to the heads of Facebook and Google about the issue on February 14. Facebook responded that it was looking at ways to reduce the visibility of anti-vaccine content.
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