People who 'like' or comment on bogus Covid-19 information will now be identified by Facebook and shown links to World Health Organisation (WHO) content on debunked myths.
The move is an escalation in Facebook's response to clamp down on "harmful" rumours and misinformation.
"People will start seeing these messages in the coming weeks," said Guy Rosen, Facebook vice-president for integrity.
"We're going to start showing messages in News Feed to people who have liked, reacted or commented on harmful misinformation about Covid-19 that we have since removed.
"These messages will connect people to Covid-19 myths debunked by the WHO, including ones we've removed from our platform for leading to imminent physical harm.
"We want to connect people who may have interacted with harmful misinformation about the virus with the truth from authoritative sources in case they see or hear these claims again off of Facebook."
In some cases, Facebook said, misinformation was getting people to drink bleach as a Covid-19 remedy.
"We've taken down hundreds of thousands of pieces of misinformation related to Covid-19, including theories like drinking bleach cures the virus or that physical distancing is ineffective at preventing the disease from spreading," said Facebook CEO Mark Zuckerberg.
"For other misinformation, once it is rated false by fact-checkers, we reduce its distribution, apply warning labels with more context and find duplicates."
He said Facebook displayed warnings on "about" 40 million posts related to Covid-19 in March, based on 4,000 articles reviewed by independent fact-checkers.
"Anyone who searches for 'coronavirus' on Facebook or Instagram is directed to the HSE website," said a spokesperson for an Irish arm of the company. "We are giving the HSE free ads for their information campaign across Facebook or Instagram."
Irish mobile operators say they are increasingly concerned at the risk of attacks on equipment as misinformation about 5G continues to circulate. While Facebook and YouTube say they will remove posts and videos that lead to damage or danger, conspiracy theorists are operating in plain sight on the platforms.