Two-thirds of anti-vaccination propaganda posted online is created by just 12 so-called influencers, research has found.
Different to those who describe themselves vaccine hesitant, anti-vaxxers tend to employ aggressive methods to persuade others not to get injections designed to help prevent disease.
The list was compiled by the Centre for Countering Digital Hate (CCDH) and found most of the figures, who claim to be political or medical leaders, are based in America.
After social media companies were made aware of the prevalence of the material some was removed, but many videos and articles remain online today.
Critics believe some are exploiting loopholes which mean that if they post content under another name or appear on a page hosted by another user their anti-vax content is not removed.