The 2014-15 measles outbreak that began at Disneyland in California and was eventually linked to an estimated 125 U.S. cases highlighted the issue of vaccine mistrust in the United States. Among those affected, 28 people were intentionally unvaccinated because of personal beliefs. But resistance to immunization is nothing new. The Anti-Vaccination Society of America, a group active from the late 1800s to the early 1900s, disputed smallpox vaccination. And more recently, a 1998 paper in the Lancet, later deemed fraudulent and retracted by the journal, asserted an association between the combined measles-mumps-rubella vaccine and autism, igniting widespread public fear that continues today.

Various factors have been found to contribute to "vaccine hesitancy"-defined by researchers as either delay or refusal of vaccination in the face of offered vaccine services. These factors include parents' perception of the usefulness of vaccines; clinicians' recommendations; public health policies; social norms; trust in vaccines, providers, and the health care system; and religious beliefs.

Two states, California and Washington, have taken steps to improve vaccination compliance-with measurable success. In July 2016, California passed legislation eliminating the "personal belief" exemption from mandatory vaccination for children attending public and private schools and licensed daycare centers. Now, only medically based exemptions are permitted. According to the California Department of Public Health, the percentage of kindergarten students who received all required vaccines rose from 93% during the 2015-16 school year to 96% during the 2016-17 school year.

In Washington, a public-private partnership of health organizations formed in 2008 introduced the "Immunity Community," a three-year intervention that encouraged parents who value immunization to engage peers through social media, school and community events, and educational materials, and to have one-on-one conversation with vaccine-hesitant parents. Following the initiative, the percentage of parents concerned about other parents not vaccinating their children rose from 81.2% to 88.6%, and the percentage of parents who believed that the ingredients in vaccines are safe went up from 72.1% to 78.2%.

Even in the absence of such statewide initiatives, nurses can play an important role in improving public understanding of the benefits of vaccination, especially school nurses. For practical how-to advice, Nichole Bobo, director of nursing education at the National Association of School Nurses, recommends the Centers for Disease Control and Prevention and the Community Preventive Services Task Force-an independent, nonfederal panel of public health and prevention experts. Both "provide evidence-based strategies to increase vaccine uptake-strategies that school nurses are well positioned to implement within their school communities," Bobo told AJN.

Among the task force's recommended interventions are home visits; vaccination programs in schools; client reminder systems; vaccination requirements for school, daycare, and college attendance; and community-based interventions. According to Bobo, school nurses can advocate for school-located vaccination services, promote both required and recommended vaccines, and "advocate for full access to state immunization information systems to identify gaps in vaccine uptake and guide decisions for next steps."

For now, the problem of inadequate vaccination coverage persists, as demonstrated by the latest outbreak of measles, this time in Minnesota. As of May 30, there were 68 confirmed cases, primarily in Hennepin County among Somali Americans. According to the Minnesota Department of Health, of the 68 people affected thus far, 64 were unvaccinated.-Dalia Sofer