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For Immediate Release
February 16, 2004

To Be or Not To Be Vaccinated: Risk Acceptance Depends on What You Do and Don't Know, Researcher Says

In general, people in the United States view vaccines as safe. But that perception may change when questions are raised about what public health officials don't know about vaccines, research suggests.

This microscope image shows the smallpox virus. Possible uses of the virus as a bioterrorism agent led to a controversial vaccination program for emergency responders and medical personnel
Image Credit: Centers for Disease Control and Prevention

That is a phenomena noted in general risk acceptability studies and readily applies to vaccination, says Ann Bostrom, a Georgia Institute of Technology associate professor of public policy. She presented research on vaccine risk acceptability February 14 at a seminar "Public Perception of Vaccination Risks" at the American Association for the Advancement of Science (AAAS) annual meeting in Seattle.

"People avoid ambiguity," Bostrom said. "They perceive risks that are unfamiliar as less acceptable than risks that are familiar, in general."

Risk perception and acceptability are also dependent on context - both personal and societal, she notes. First-hand experience with adverse reactions to vaccines, for example, affects a person's risk acceptance. Bostrom cited evidence from collaborative research she and her colleagues will publish later this year.

Beyond describing the factors that affect individual choices regarding vaccine risk acceptance, Bostrom also described the sometimes-controversial public decision-making process on vaccination policy.

"Controversy isn't always a bad thing," she explained. "Conflicts of interest can be real, and both scientific and policy processes should be scrutinized. Science, and in particular the science that has enabled vaccine development, has given us much longer, healthier lives. But engineering our immune systems is no mean task, and thinking broadly about that bigger picture is important."

She also notes that individual and public decision-making processes about vaccines are sometimes at odds. For example, a hypothetical vaccination policy might be chosen to minimize disease risk to the public as a whole, while increasing the risk to some small sub-population that is susceptible to a vaccine risk.

Georgia Tech researcher Ann Bostrom has found that the acceptance of vaccination risk depends on how much people do and don't know about it.
Georgia Tech Photo

"The ideal of using both analytic and deliberative processes to reach agreement (not necessarily consensus) on what society should do is one many hold high," Bostrom said. "The aim is to find ways of improving both individual and collective welfare. If the risk to some sensitive sub-populations is high, then a policy that doesn't require their immunization with that vaccine is, of course, preferable to another policy, all else equal.

"It's problematic when goals and values in public health appear to differ from individuals' goals - for example when cost-effectiveness appears to be driving health policies, whereas parents are only concerned about the health of their children," she added.

Bostrom drew evidence about risk acceptance from a paper she and her colleagues wrote on engineered mitigation of earthquake consequences. In a review of research on the topic, Bostrom suggests that potential injuries and deaths from earthquake-related building collapse, for example, are likely to be valued differently depending on factors such as who might be injured or die, and recent experience.

Like decisions about vaccination, risk-acceptance decisions about earthquake mitigation are made in complex decision contexts involving multiple stakeholders with multiple values, Bostrom notes. They require both technical analysis and deliberation on the differing values and competing interests. "Value elicitation should influence solution design, and the process of designing solutions can lead to clearer value articulation," she wrote in the paper.

Bostrom also cited a study in which she and her colleagues examined trust in information sources about smallpox vaccine or disease. They also studied participants' behavioral intentions about and mental conceptions of the controversial vaccine, which has shown the potential for serious, even fatal, side effects. It is no longer routinely administered in the United States because the disease has been eliminated worldwide since 1977. But in 2002, bioterrorism fears prompted a voluntary smallpox vaccination program for emergency responders and medical personnel, and a mandatory program for some military personnel.

Bostrom's study compared the survey responses of 24 Georgia Tech students with those from a recent national survey of more than 1,000 adults conducted by Harvard University researchers. Bostrom found:

  • Neither group surveyed is thinking much about or looking for information about smallpox vaccine or disease.
  • The Georgia Tech students appear to trust medical technology and expertise more than the general public and are less concerned about the vaccine than the larger population.
  • Both lack of information and misconceptions, as well as trust, appear to have influenced the students' behavioral intentions about the vaccine.

"Despite what has been portrayed in the media as the catastrophic potential of a smallpox bioweapon, in this context, trust seems driven less by any conscious comparison of specific values and more by general, previously determined attitudes toward technology, expertise and government," Bostrom reported.

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TECHNICAL CONTACT: Ann Bostrom (404-894-9629); E-mail: (

WRITER: Jane Sanders