Eighteen states, including Arizona, allow nonmedical exemptions from school immunization requirements, which has led to falling vaccination rates in twelve of those states. A study by the Baylor College of Medicine shows Arizona in the crosshairs.

According to the study, anti-vaccine movements appear to be a Western phenomenon. Several hotspots stand out for nonmedical exemptions, and Maricopa County is one of them, with nearly 3,000 exemptions for kindergarten students.

Peter Hotez, dean for the National School of Tropical Medicine at Baylor, said part of the problem is false information on the internet.

“What’s happening now across the country, but more in Western states, is that parents read this false information on the internet. They come into the pediatrician’s office and cite all of these false or misleading bits of information, and the pediatrician needs now to know how to deal with them," he said. 

Hotez said falling immunization rates may threaten herd immunity, and that continuing education about vaccinations is needed.