In late 2015, Italian virologist Roberto Burioni took part in a Q&A with young mothers on a Facebook group and was alarmed to find many of them spouting conspiracy theories about vaccinations. The measles shot, they said, gives children autism.

The 55-year-old decided to take a deeper look online and realized there was an ecosystem of Italian anti-vaccination groups on the social media site. In spring 2016, Burioni sat down, fired up his laptop and began debunking anti-vaccination conspiracy theories on his public Facebook page.

“I started writing because I was fed up of social media being at the hands of people telling lies,” Burioni, who is a professor of microbiology and virology at the Vita-Salute University San Raffaele, Milan, says during a phone interview. “All the voices [online] in Italy were against vaccination. There was no debate and I did what I could to start one.”

Just over two years later that debate has gone from an online feud to a live political issue in the Italian general election due on March 4. As skepticism about vaccines has become widespread in Italy, so-called “anti-vaxxers” have become a voting bloc for the populist parties vying for votes. As a result, two of the leading populist parties — the far-right League (formerly the Northern League) and the anti-establishment Five Star Movement (5SM) — have pledged, if elected, to scrap a law passed in July that made ten vaccinations compulsory for children under the age of 16. If they do, health experts warn it could be a huge step backwards in the global fight for children’s health.

Vaccine skepticism in Italy dates back to a debunked 1998 study by Andrew Wakefield that linked the Measles, Mumps and Rubella (MMR) shot typically given to children after their first birthday to autism. The discredited idea took hold among an “intellectual fringe” in Italy, says Andrea Grignolio, a medicine historian at the La Sapienza University of Rome. The skeptics tend to be “rich and older parents,” he says, “who are susceptible to both alternative treatments, like homeopathy, and conspiracy theories.”

The waters surrounding the issue of vaccination were muddied further by a 2012 court ruling in the city of Rimini, northeast Italy, that a child’s autism had in fact been caused by the MMR vaccination. The Rimini ruling was overturned in 2015, but the judgement had by then done its damage. According to Grignolio, vaccine skeptics today make up 5% of the population while vaccine hesitancy— which the WHO defines as a “delay in acceptance or refusal of vaccines despite availability of vaccine services”— is estimated to affect a further 10% of Italy’s 60 million-strong population. ‘That’s millions of people,” Grignolio says.

It shouldn’t be a huge surprise, then, that measles has made a troubling comeback in Italy. Cases jumped nearly six-fold from around 870 cases in 2016 to more than 5,000 cases last year. In the last six months of 2017, Italy was ranked sixth-highest worldwide in measles cases after India, Nigeria, the Ukraine and China. The mandatory vaccine legislation, nicknamed the Lorenzin law after the country’s health minister Beatrice Lorenzin, was introduced last year to combat the troubling increase.

Riccardo Saporiti, an Italian journalist who has written widely about the issue, traces the widespread distrust of medical orthodoxy back to corruption scandals that eroded faith in the state more generally. “Italians first started not trusting their politicians in the ’90s, then we lost faith in doctors and economists,” Saporiti says. “Now when it comes to vaccines, everyone has an opinion on it.”

Now, a new generation of political parties has emerged in Italy seeking to capitalize on that loss of faith in institutions — and they have focused on the issue of vaccines as a potential vote-winner in the tight electoral contest. Beppe Grillo, the founder of 5SM, which is currently the biggest single party in the polls with around 29% of the vote, first questioned the wisdom of vaccines in a 2015 blog post. “Vaccines have played a fundamental role in eradicating terrible illnesses such as polio, diphtheria and hepatitis,” Grillo wrote, the Guardian reports. “However, they bring a risk associated with side effects that are usually temporary and surmountable… but in very rare cases, can be as severe as getting the same disease you’re trying to be immune to.” The party proposed a law that year outlawing vaccines.

Under new leader Luigi Di Maio, the 5SM has since cut a more moderate tone, bringing academics on as board advisors and saying it merely wants to cut the number of mandatory vaccines from 10 to four. But 5SM candidate Roberta Lombardi, who is running as to lead Rome’s regional government of Lazio, recently tweeted that she would do away with compulsory vaccinations if elected President of Lazio.

The more extreme position on vaccines is held by the League, a far-right party set to play a key role in any center-right coalition that emerges after the March 4 vote. The party is entirely opposed to the law. The party’s leader Matteo Salvini argues mandatory vaccinations incurs on Italians’ “freedom of choice,” saying in a recent interview that “having twelve [shots] together exposes the children [to] risk” and the jabs should be at the discretion of “of mum and dad.”

That’s a first step toward getting rid of the vaccine completely, says medical historian Grignolio. “It is an intelligent strategy. If you say you are against [it], then [revoke] compulsory vaccinations, what you are offering is a route for citizens to avoid vaccinations.” Comilva, one of the country’s largest anti-vaccination bodies has endorsed the League. In an email to TIME, Claudio Simion, president of Comilva, said 5SM’s leadership has betrayed “the will of the base,” but added approvingly that there are still “members of the party who continue to support our struggle for freedom of choice and transparency.”

The anti-vaxxers won’t determine this election. Immigration, corruption and unemployment rank higher on voters’ lists, according to a Feb. 14 survey from LUISS Guido Carli in Rome. Only 22% of the 6,000 people polled said removing mandatory vaccines was a voting priority.

But if Italy’s next government decides to scrap the law, it could have real human effects. The WHO says 95% of the population needs to be vaccinated in order to be protected from measles, but child immunization rates dropped from 90% in 2013 to 85% in 2015. If the national figure remains or drops below 85% the impact would be felt across Italy and beyond, warns Robb Butler, WHO’s Europe head of vaccine-preventable diseases and immunization. “We will see outbreaks, we will see deaths, we will see Italians exporting cases to other countries, who will then suffer outbreaks because Italy is exporting measles,” he says.

Skepticism is still rife. In the most vaccine-skeptic areas of the country, like the northeastern region of Bolzano, vaccine coverage dropped to around 67% last year. Meanwhile, a nurse in northern Italy was accused in 2017 of administering fake vaccinations between 2009 and 2015. She is currently under investigation and up to 20,000 children are thought to be at risk of infectious diseases.

To politicize the issue of vaccinations when that number of lives is at risk is the height of irresponsibility, Butler says. “It is totally unacceptable when public health, particularly childhood immunization, is used as political leverage. But in many countries it is — and those are the countries that are struggling the most.”

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.