Armed with little more than a healthy respect for science and some SpongeBob SquarePants memes, a handful of Australians go online each day to take on a dedicated foe.

The anti-vaccination movement was not invented by the internet, but its spread has been aided by the controversy-addicted algorithms of digital platforms like YouTube and Facebook.

Social media companies have been slow to act — Facebook continues to accept paid ads from vaccination sceptic groups such as the Australian Vaccination-risks Network — and in the vacuum, volunteers log on during lunch breaks to make a point: there is no established link between vaccines and autism.

A sponsored ad on Facebook from the Australian Vaccination-risks Network. ( ABC News: Facebook screenshot )

Simon*, a West Australian early childhood educator, helps run the Facebook page Refutations to Anti-Vaccination Memes. He did not want to include his real name due to incidents where people have been harassed by anti-vaccination advocates.

He described running the Facebook page as "an engrossing hobby". Dealing in pro-vaccine images from the darkly humorous to the occasionally brutal as well as the informational, it has been around since 2012.

The Refutations to Anti-Vaccination Memes page does "unmercifully mock" what he calls the hard-core "anti-vaxxers" and especially their leaders. The goal is not to convince settled members of the anti-vaccination community. It's to marginalise them.

"We want people to find the very idea of being or becoming anti-vax laughable, something that no reasonable person would ever want to be perceived as being," Simon said.

But should unpaid Australians carry the load for Facebook when it comes to combatting a trend the World Health Organisation has named among the top threats to global health?

The answer is clearly no — but fighting vaccine hesitancy is more complex than turning off the Newsfeed tap.

De-monetise, de-platform

Vaccination is an irresistible controversy. It sits right between bodily autonomy and personal liberty versus societal good, Dr Jessica Kaufman suggested.

A public health researcher at the Murdoch Children's Research Institute, she pointed out that unlike political misinformation, the consequences of avoiding vaccines can be tangible. Measles is obvious.

"People get sick because they don't get vaccinated," she said.

A meme shared on the Refutations to Anti-Vaccine Memes page. ( ABC News: Refutations to Anti-Vaccine Memes screenshot )

Dr David Hawkes, a molecular virologist in Melbourne, helps administer the Stop the Australian (Anti)Vaccination Network Facebook page and has followed the movement closely.

The page targets the Australian Vaccination-risks Network, which has lobbied against mandatory vaccination for decades, among other organisations. The group also tries to stop Australian tours by prominent anti-vaccination groups and spokespeople.

"You should not take medical advice from a Facebook site, and that's our point," he said.

In fact, anti-vaccination messages have become enough of a reputational liability that some social media platforms are acting.

YouTube recently removed advertising from anti-vaccination videos, and since 2017, Pinterest has blocked some search terms relating to vaccination.

Pinterest's tactic — deemed "digital de-platforming" by Dr Naomi Smith, a lecturer in digital sociology at Federation University — is not a solution Dr Hawkes is entirely comfortable with.

While he supports taking a page like Australian Vaccination-risks Network off Facebook, for example, he believes it's important to have groups where people discuss vaccinations and have their fears addressed.

Dr Kaufman also questioned whether removing oxygen from the movement by shutting down search, as Pinterest has done, is the best solution.

People who are hesitant about vaccines, she suggested, often hold other conspiratorial beliefs. Banning conversations about the issue is likely to feed fears of censorship.

"All these authority figures come together in some people's minds: medicine, the government, media," she said.

"If all of those people are working together to silence this side of things, that's not going to convince them that vaccines are perfectly safe."

Whose job is it?

As the pro-vaccination Facebook community continues the fight, their effectiveness is difficult to measure.

Dr Smith observed that the two communities appear mostly to exist in separate bubbles, talking to people on either side who are already convinced. Exchanges seem "antagonistic or dismissive".

Memes making fun of anti-vaccination advocates are common on Facebook. ( ABC News: Refutations to Anti-Vaccine Memes screenshot )

Tweaking social media algorithms so that they funnel people towards good information, rather than silencing conspiracy theorists, might be a more helpful better option, Dr Kaufman added.

A Facebook spokesperson said the platform knows it has more work to do, and will soon announce additional changes to reduce the distribution of health-related misinformation.

As it is, the direct impact of social media and anti-vaccination messages on Australia's vaccination rate is still largely unclear. In December 2018, Australia's national immunisation coverage rate for all five-year-olds had increased to 94.67 per cent from 79.39 per cent in 2008.

Nevertheless, a small number of people on social media can make a lot of noise, and anti-vaccination messages can be obscured by rhetoric around "safe vaccines" or "vaccine choice".

The seeds of doubt may be planted on Facebook but doctors suggest the hard, slow work of convincing people that immunisation is important is done in person.

For Simon, fighting the anti-vaccination movement online "makes me feel like I'm doing something worthwhile".

"Probably most importantly, we want to reach the silent majority of people who are basically pro-vaccines," he said.