Pediatrician Avis Meeks Day examines a girl at the Austin Regional Clinic. The Texas clinic adopted a policy in 2015 that it would no longer accept new patients who aren’t getting fully vaccinated. (Austin Regional Clinic and Leindani Creative) When it comes to persuading parents in the United States who are hesitant about vaccinating their children, the public health messages often rely on facts and science to explain how immunization not only protects those children but also shields other vulnerable people from dangerous infectious diseases. But information campaigns that emphasize fairness or preventing harm sometimes backfire and can worsen vaccine hesitancy, research has shown. A study published Monday in Nature Human Behaviour suggests a more effective way to reach vaccine-hesitant parents may be to focus on two potentially powerful moral values that underlie people’s attitudes and judgments: individual liberty and purity. Compared with parents who approve of vaccines, parents who are most reluctant to vaccinate are strongly concerned with liberty and purity, the researchers found. In this framework, liberty is associated with belief in personal responsibility, freedom, property rights and resistance to state involvement in citizens’ lives. Concerns about purity center on boundaries and protection from contamination. Although the vast majority of parents across the country vaccinate their children and follow recommended schedules for this basic preventive-medicine practice, vaccine skepticism and outright refusal in recent years have led to places where there are communities of undervaccinated children who are more susceptible to disease and pose health risks to the broader public. Minnesota's measles outbreak in the spring sickened 79 people and exposed 8,000 to the virus, including more than 500 people who were asked to stay home from school, child care or work because they were unvaccinated and at risk of contracting and spreading the disease. The new study used a social psychology theory known as Moral Foundations Theory to assess the underlying moral values most strongly associated with vaccine-hesitant parents. Their findings correspond with the