Another reason many late-thirtysomethings didn't get flu shots despite their knowledge of the risks posed by swine flu is that they often display a trait well-known in adolescents.
"Today, the feeling of invincibility can last well into the 20s or 30s," said Fran Walfish, a Beverly Hills-based psychotherapist and author of "The Self-Aware Parent."
"A lot of people have not matured as quickly as we would hope and one of the issues that is prevalent in adolescents and many adults is a certain level of belief that they are omnipotent and more powerful than things out there."
Miller hopes the study's findings can shed some light on better ways to reach out to Generation Xers when it comes to preparing for future epidemics.
"I think we need to do a much better job getting everybody to understand about influenza and viruses," he said.