The company already bans ads about vaccine "hoaxes" such as the false idea vaccinations cause autism. The latest policy expands that to those which discourage vaccines for any reason.

But Facebook also said on Tuesday ads that "advocate for or against legislation or government policies around vaccines" including a COVID-19 vaccine, will still be allowed.

They will still have to be approved by the company as political advertisements and include a "paid for by" label on who is funding them.

And unpaid posts by people or groups that discourage vaccinations will also still be allowed - the new policy only includes paid advertisements.

The social network said it will also run an information campaign encouraging people to get flu shots this year.

Facebook has taken other steps to try to stop the spread of vaccine and coronavirus-related misinformation on its platform.

Last year, it said it would begin hiding groups and pages that spread misinformation about vaccinations from the search function of its site.

Since the pandemic began, the company has tightened rules around COVID-related misinformation.

For instance, it promotes articles that debunk COVID-19 misinformation, of which there are thousands, on a new information centre called Get The Facts.

It also bans what it deems "dangerous" misinformation about the virus and has removed posts by President Donald Trump under this policy.

Some experts were sceptical about the move.

Facebook is addressing the anti-vaxxers of 2014 and 2015 and not the anti-vaxxers of 2020, said David A. Broniatowski, an associate professor at George Washington University who has published several studies on vaccine misinformation.

Broniatowski published a study in 2019 that found that the majority of anti-vaccine misinformation being pushed in advertisements on Facebook were coming from two groups, including one led by Robert F. Kennedy Jr and a California-based organisation called Stop Mandatory Vaccination.

Australian Associated Press