The research, published in PLOS Medicine this week, identified areas with high immunization exemption rates, which are more susceptible to epidemics of diseases like measles and whooping cough.
Child receiving vaccine
Credit: Andrew Brookes/Getty Images

Vaccination continues to set off fiery debate among parents around the country. Now, a new analysis, published on Tuesday in PLOS Medicine, highlightsareas around the U.S. where the risk of measles and other vaccine-preventable childhood diseases is greater, because more parents in those locations hesitate or refuse to get their children immunized.

According to The Washington Post, 18 states let parents opt out of school immunization requirements for nonmedical reasons, with exemptions for religious or philosophical beliefs. And in two-thirds of those states, the report found that a growing number of kindergartners have not been vaccinated.

For the report, researchers from several Texas academic centers tracked the increasing number of children with exemptions in all 18 states from the 2009-2010 to 2016-2017 school years. They defined many rural, as well as urban, areas as "hotspots," given their high exemption rates, which make them more susceptible to epidemics of pediatric infectious diseases like measles and whooping cough.

One state in particular has eight of the top 10 counties with the highest exemption rates: Idaho. Two more with particularly high exemption rates: Wisconsin and Utah. And researchers also concluded that the 10 counties with the highest exemption rates were in rural areas, with populations of less than 50,000.

But plenty of urban areas are considered hotspots, as well. When it came to counties where more than 400 kindergartners received nonmedical exemptions in 2016-2017, the 15 cities with the most exemptions were: Seattle and Spokane, Wash.; Portland, Ore.; Phoenix; Salt Lake City and Provo, Utah; Houston, Fort Worth, Austin and Plano, Tex.; Detroit, Troy and Warren, Mich.; Kansas City, Mo.; and Pittsburgh.

Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine and one of the study authors, told The Washington Post that the he and his colleagues identified "some scary trends."

Researchers are also hoping to do a follow-up study on social and demographic factors behind the high exemption rates in some of the rural areas. In the meantime, Hotez hopes federal health agencies, such as the CDC, begin investigations.

This urgency is underscored by the concern that, according to the report, the number of exemptions in those densely populated (not to mention locations of busy international airports) metropolitan areas could lead to “outbreaks of vaccine-preventable diseases [that] could either originate from or spread rapidly throughout these populations of unimmunized, unprotected children."

The good news: Vaccination rates remain high overall nationally, the Washington Post notes. Yet, experts are given pause over the fact that some communities' vaccine coverage is slipping below the level of 90 to 95%.

"It’s alarming to see the rise in exemption rates across this country, putting communities at greater risk,” said Amy Pisani, director of the vaccine-advocacy organization Every Child By Two, told the Post. “Parents need to understand that timely vaccines are critical to protecting children's health and should be at the top of the family’s to-do list."