Facebook groups are using the carrot emoji to hide anti-vax content from automated fact-checking by algorithms.
The BBC has seen several groups, one with hundreds of thousands of members, in which the emoji appears instead of the word "vaccine".
Facebook algorithms tend to focus on words rather than images.
The groups are being used to share unverified claims of people being injured or killed by vaccines.
After the BBC notified Facebook's parent company, Meta, the groups were removed.
"We have removed this group for violating our harmful misinformation policies and will review any other similar content in line with this policy. We continue to work closely with public health experts and the UK Government to further tackle Covid vaccine misinformation," the firm said in a statement.
However, the groups have since reappeared in our research.
One group we saw has existed for three years, but was renamed to focus on vaccine stories, from being a group for sharing “jokes, bets, and funny videos” in August 2022.
The very large group's rules say: "Use code words for everything." It adds: "Never use the c-word, the v-word, or the b-word" (covid, vaccine, booster). It was created more than a year ago and has more than 250,000 members.
Marc Owen-Jones, a disinformation researcher and associate professor at Hamad Bin Khalifa University in Qatar, was invited to join her.
"There were people reporting on relatives who had died shortly after getting the Covid-19 vaccine," he said. "But instead of using the words 'Covid-19' or 'vaccine,' they were using carrot emojis."
"I was a little confused at first. And after I clicked – I saw that it was being used as a way to avoid, or apparently circumvent, Facebook's fake news detection algorithms."
(Full article by BBC available in English)