The percentage of kindergarten-aged children receiving non-medical vaccine exemptions has risen, forming so-called "hotspots" where diseases could originate or quickly spread, according to a study published Tuesday in PLOS Medicine.
Peter Hotez, dean of Baylor College of Medicine's National School of Tropical Medicine and a co-author of the report, said personal, or "philosophical," exemptions to vaccines led to a measles outbreak in California in 2014 to 2015, and the California Legislature as a result subsequently eliminated such exemptions. However, he said 18 states still allow individuals to seek personal vaccine exemptions.
Hotez said he and his team "wanted to see what was going on in the 18 states that still allow philosophical exemptions." To do so, the researchers looked at vaccination data from CDC and state health departments for school years starting from 2009-2010 through 2016-2017 from the 18 states that allow personal vaccine exemptions.
According to the researchers, there was "an overall upward trend of enrolling kindergarteners with non-medical exemptions" from 2009 to 2014 in 12 of the 18 states that allow personal vaccine exemptions.
The researchers also ranked the top 10 counties where non-medical exemption vaccination rates were highest among the 18 states that permit them, and found that eight of those counties were located in Idaho. For instance, the researchers found that 27% of kindergarten students in Idaho's Camas County claimed personal vaccine exemptions in the 2016-2017 school year.
The researchers wrote that high rates of personal vaccine exemptions in those areas "suggest that outbreaks of vaccine-preventable diseases could either originate from or spread rapidly throughout these populations of unimmunized, unprotected children."
Overall, the researchers found that six states had total non-medical vaccine exemption rates nearing or exceeding 5%, which could start to jeopardize herd immunity, which requires a vaccination rate of between 90% and 95%. Those states are:
- Utah; and
Hotez said, "Vaccine exemptions for reasons of personal belief have caused a lot of damage in terms of facilitating breakthrough measles epidemics," noting California's measles outbreak and a similar outbreak that occurred last year in Minnesota. "In both instances, vaccine coverage declined due to organized anti-vaccine movements alleging that vaccines cause autism and other illnesses, despite overwhelming scientific evidence that there is no link."
Hotez called for more research to identify what might be driving personal vaccine exemption rates in the "hotspot" areas, and speculated that "well-organized anti-vaccine activities" might be part of the answer.
Saad Omer—a professor of global health, epidemiology and pediatrics at Emory University—said the study provides a deep look at where areas with high vaccine exemption rates exist. "We may have known about hot spots, but this is a little more systematic look," he said.
Amy Pisani, director of the vaccine-advocacy organization Every Child By Two, called the findings "alarming." She said, "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" (Walker, MedPage Today, 6/12; Rapaport, Reuters, 6/12; Sun, "To Your Health," Washington Post, 6/12; Olive et al., PLOS Medicine, 6/12).
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