Thanks to an effective vaccination program, measles was declared eliminated in the United States in 2000. However, the highly contagious virus continues to circulate in many regions of the world and reentered the United States through infected travelers from countries experiencing measles outbreaks. This has resulted in several recent U.S. outbreaks in communities with pockets of unvaccinated people.
Measles outbreaks can be controlled by herd, or community, immunity. Herd immunity exists when a sufficient proportion of a population (in the case of measles, more than 94%) is immune to an infectious disease by vaccination or previous infection, thereby making person-to-person spread unlikely. Unvaccinated newborns and those with chronic illnesses are then offered some protection because the disease is less likely to spread within the community.
Earlier this year, UNICEF warned that global cases of measles are increasing to alarmingly high levels, with significant outbreaks in Israel, the Philippines, and Ukraine. Nine measles outbreaks have occurred in the United States since 2018, with a total of 764 cases reported to the Centers for Disease Control and Prevention as of May 2019. These outbreaks are centered in unvaccinated communities and have been linked to travelers from countries with ongoing measles outbreaks. Most of the U.S. cases are in New York City and adjacent Rockland County.
All U.S. states and the District of Columbia have school immunization laws requiring specific vaccines for students, with exemptions for medical reasons. However, according to the National Conference of State Legislatures, 47 states still allow parents to opt out of vaccinations because of religious beliefs, and 17 states allow philosophical exemptions for personal or moral reasons.
Current data do not support concerns about risks from vaccines. Yet some antivaccination groups propagate unproven claims regarding vaccines, undermining parents' trust in the health care profession. And some have recently subjected provaccine experts to harassment campaigns via social media.
The World Health Organization lists vaccine hesitancy as one of 10 global health threats in 2019. This reluctance, despite the availability of effective vaccines, threatens to reverse progress made against vaccine-preventable diseases. The problem of parental refusal of immunization for children is an important one for health care providers who are a source of immunization information for parents. The American Academy of Pediatrics advises health care providers to address vaccine hesitancy by listening to parental concerns and discussing the risks of nonvaccination.
Incentivizing school districts to improve vaccination rates and making it procedurally difficult for parents to opt out are among several immunization strategies suggested by Alison Buttenheim, associate professor of nursing and assistant professor of health policy in the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. For a summary of the issues and ways to address them, view her video on the topic at http://www.youtube.com/watch?v=NOkKKNOFS7E.-Barbara A. Goldrick, PhD, MPH, RN, FSHEA