Instagram says it will block hashtags being used to spread "verifiably false" information about vaccinations.
The social network already blocks hashtags that are themselves false claims, such as #vaccinescauseautism.
It says it will now block more general hashtags that are being used to spread lies by so-called anti-vaxxers.
However, several anti-vaccine topics and accounts spreading misinformation and hoaxes are still active on Instagram.
Hoaxes not hoaxers
Instagram told the BBC it will not take action against people or accounts who identify themselves as anti-vaxxers.
However, it will work to limit the spread of provably false claims because these have real-world harmful effects on the public.
It said it relied on global authorities such as the World Health Organization and the US Centers for Disease Control and Prevention to identify hoaxes.
False claims such as #vaccinescauseaids and #vaccinesarepoison are already banned and return no search results on Instagram.from-bbc.com