9/11 'Truthers' Are More Likely To Be Anti-Vaxxers, Too

yellow fever vaccine
A woman gets a vaccine against yellow fever at an outpatient clinic in Sao Paulo, Brazil on January 12, 2018. MIGUEL SCHINCARIOL/AFP/Getty Images

People who believe conspiracy theories about President John F. Kennedy's assassination, the death of Princess Diana, a New World Order and 9/11 are also more likely to be skeptical of vaccines, new research published Thursday in Health Psychology has found.

University of Queensland researchers surveyed more than 5,000 people in 24 different countries about their belief in those four conspiracy theories, their disgust of blood and needles, and their worldviews, among other things. They found that all of these factors were related to a person's attitude toward vaccination far more than their level of education or their gender. The study did not ask people whether or not they had been vaccinated themselves, but rather about their opinions on vaccines' safety and the schedule on which they are administered.

Specifically, in Australia, Canada, Germany, New Zealand, U.K. and the United States, people's attitude towards conspiracy theories was responsible for about a quarter of the total difference observed between people's attitude towards vaccinations.

"We know that conspiracy theories do influence what people think and what they do," Karen Douglas, a social psychologist at the University of Kent who was not involved in the research, told Newsweek. "For it to be consistent across all of these countries, it's something that's quite important to take further."

anti vax france injection
A doctor injects a vaccine to a baby on October 31, 2017 in Quimper, France. The French Assembly voted on October 27 to expand the number of mandatory vaccinations for children from three to eleven, a measure which anti-vaccine groups challenged. FRED TANNEAU/AFP/Getty Images

Douglas's own work has focused on conspiracy theories about vaccines themselves. In addition to the false and refuted link between vaccines and autism, other theories encourage people to believe that pharmaceutical companies are hiding safety issues. "This might also happen in collusion with the government, depending on which conspiracy theory you listen to," Douglas said.

Some of the findings in this latest study echo another published in December, namely people who had an "individualistic" view of the world were also more likely to be hesitant around vaccines. This newer study found that worldview was less correlated with vaccine hesitancy than other things, like belief in conspiracy theories.

But translating knowledge about what psychological processes might underpin vaccination hesitancy into a way to encourage people to vaccinate is still tricky. Exposing people to information about vaccines before they read conspiracy theories seems to protect them.

"Once these ideas have taken root, once people believe in conspiracy theories," Douglas said, "and even once they've read about them, they take this information on board, that information is very difficult to refute."