Researchers from the University of Missouri have found that if a vaccine that protects against HIV and other sexually transmitted infections (STIs) were available, college students who believe themselves to be physically invulnerable, or “invincible,” would be less likely to seek it out, ScienceDaily reports.

According to the article, the study measured two vulnerability factors: physical and psychological danger. Researchers discovered that those students who were psychologically invulnerable, or who did not care what others thought about them, were more likely to get the vaccine. Those who did not perceive themselves to be in danger of physical harm, conversely, were less likely to get vaccinated.

In the study, led by Russell Ravert at the university’s College of Human Environmental Sciences, perceived susceptibility to contracting HIV was the strongest predictor of vaccine acceptance, followed by their number of sexual partners. Cost of the vaccine was also considered.

“It is important to determine what factors are associated with vaccine acceptance because not all students will be willing to take vaccines," Ravert said. "Efforts to promote vaccines should consider that students who aren’t worried about being harmed are less likely to get the vaccine, even when it’s warranted by their sexual behavior.”