(Newsweek) Despite overwhelming scientific evidence that vaccines are a safe and effective tool for the prevention of childhood diseases, a significant minority of the U.S. population remains skeptical of the practice, as evidenced by the persistence of the anti-vax movement.

This has sometimes made it a difficult task to achieve the desired level of coverage required for the protective effects of “herd immunity” to kick in. Now, researchers from Dartmouth College have investigated this phenomenon, uncovering a key factor in why it may be so hard to increase the numbers of people being vaccinated.

In a study published in the journal Proceedings of the Royal Society B, Feng Fu, an assistant professor of mathematics, and colleagues showed that a phenomenon known as “hysteresis” may act as a roadblock for efforts to increase vaccination rates.

Note: Read our discussion guidelines before commenting.