IN 1998 the Lancet, a medical journal, published a paper which made a claim that continues to infect public discussion: vaccines can cause autism. The article was later retracted and its primary author, a British researcher named Andrew Wakefield, lost his medical licence. In 2016, however, the disgraced doctor began receiving some rather exclusive invitations in America: first to a meeting with a presidential candidate and then to an inauguration ball in Washington, DC. He had found a willing listener in Donald Trump, who has tweeted about the dangers of vaccines more than 30 times. But theirs was not the only crossover between anti-vaxxers, as they became known, and anti-establishment politicians.

European populists have also flirted with vaccine scepticism. In France, where more than 20% of the population does not support vaccines, Marine Le Pen, of the far-right National Rally party (previously the National Front), opposes mandatory immunisations and has questioned their safety. Vaccines were also a contentious issue during elections in Italy this year, which happened during a measles outbreak that followed a drop in vaccination rates. The populist Five Star Movement (M5S) opposed new policies that increased the number of required vaccines and fined non-compliant parents. (Italy’s former health minister founded a centrist political party with the slogan “vaccinate against incompetence”.) Across Europe vaccination rates have declined and the incidence of measles has soared—up by 300% last year, reckons the World Health Organisation. Despite this increase, or perhaps in reaction to efforts to combat it, vaccine doubters remain vocal. On Vaccine Injury Awareness Day in June, thousands joined protests against compulsory vaccinations in Italy and France.

Why do anti-vaccine conspiracies seem attractive to populists? It might be because both positions involve the questioning of authority. Ms Le Pen alleged that health ministers in France were on the payrolls of vaccine laboratories. Government missteps, including a since-overturned Italian court decision in favour of a mother who claimed that vaccines had given her child autism, do not help. In America people who do not trust the government are more likely not to trust vaccines. They receive validation from websites that publish anti-vaxxer pseudoscience, and from Mr Trump, who has tweeted that “the doctors lied” and that parents “know far better than fudged up reports!” Anti-vaccination movements did not begin with these populists, but they do get fuel—and talking points—from them. In response to a question from a journalist last year, Mr Wakefield said, “I don’t talk to fake news.”

In office Mr Trump has actually done little on vaccines (the new director he picked for the Centres for Disease Control is in favour of them). The greatest gift he has given anti-vaxxers has been to recognise their argument. In Italy the new government, a coalition between M5S and the conservative League, says that state schools will no longer require written proof that children are vaccinated. In France and Germany, by contrast, where the populists are not in power, punitive policies have been launched to increase vaccination rates. These will do little however to convert anti-vaxxers. It is easy to forget the severity of deadly diseases where vaccines have largely wiped them out. Conspiracy theories may prove even harder to eradicate.