September 23, 2019 | The New York Times

How Anti-Vaccine Sentiment Took Hold in the United States

Faced with risking autism or measles, some parents thought the answer was obvious. Most had never seen measles, mumps or rubella because vaccines had nearly eliminated them. But they believed they knew autism.

And most people are notoriously poor at assessing risk, say experts in medical decision-making.

Many stumble on omission bias: “We would rather not do something and have something bad happen, than do something and have something bad happen,” explained Alison M. Buttenheim, an associate professor of nursing and health policy at the University of Pennsylvania School of Nursing.

People are flummoxed by numerical risk. “We pay more attention to numerators, such as ‘16 adverse events,’ than we do to denominators, such as ‘per million vaccine doses,’ ” Dr. Buttenheim said.

A concept called “ambiguity aversion” is also involved, she added. “Parents would like to be told that vaccines are 100 percent safe,” she said. “But that’s not a standard we hold any medical treatment to.”

Loading tweets...