British newspaper The Guardian analyzed user engagement with six popular anti-vaccination Facebook pages from July to August.
According to Business Insider, the number of users engaging with 'anti-vaxxer' content more than tripled during that period, from 12,000 to 42,000.
Facebook said the analysis wasn't reflective of the platform as a whole.
The social media platform added that it took down 7 million pieces of misinformation related to COVID-19 between April and June.
The UK is currently experiencing a second wave of coronavirus infections.
In August, a poll found just 30% of Britons said they would definitely get a coronavirus vaccine once it became available.
Some experts blame anti-vaccine misinformation and a lack of trust in the government for the low figure.