OMISSION BIAS AND PERTUSSIS VACCINATION

Background: Several laboratory studies have suggested that many people favor potentially harmful omissions over less harmful acts. The autho rs studied the role of this omission bias in parents' decisions whethe r to vaccinate their children against pertussis. Methods: Two hundred mail surveys were sent to subscribers to a magazine that had published articles favoring and opposing pertussis vaccination. Subjects were a sked about their beliefs about the vaccine and the disease, and whethe r they had vaccinated their own children or planned to, and they were given test items to identify omission bias in their reasoning. Results : One hundred and three subjects (52%) responded to the survey. Respon dents who reported they did not or would not allow their children to b e vaccinated (n = 43; 41%) were more likely to believe that vaccinatin g was more dangerous than not vaccinating (p < 0.001). They were also more likely to exhibit omission bias (p = 0.004), holding constant the ir stated beliefs about the danger of the vaccine. Conclusions: Omissi on bias plays a role in decisions not to vaccinate with pertussis vacc ine, beyond the role played by belief about the risk of vaccination.