Eighteen states allow parents to opt out their children from vaccinations required for school entry by obtaining nonmedical exemptions (NMEs) based on antivaccine beliefs, and 12 of them have had significant increases in NMEs since 2009, according to a paper in PLOS Medicine in June 2018.
The states are Arizona, Arkansas, Idaho, Maine, Minnesota, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, and Utah. High numbers of NMEs seen in large urban “hotspots” in these states (such as Phoenix, Houston, and Pittsburgh) are a major concern because vaccine-preventable diseases can spread rapidly through these populations of unimmunized children, the researchers wrote.
In recent years there have been outbreaks of diseases like measles and pertussis (whooping cough) because of inadequate “herd immunity” in schools. Herd immunity occurs when enough children get vaccinated, thereby providing a degree of protection for those who can’t be vaccinated since they’re less likely to come in contact with an infected child.
This article first appeared in the UC Berkeley Wellness Letter.