In the City of Chicago, only 88.8 percent of adolescents are covered by the Measles, Mumps and Rubella (MMR) vaccine, according to data from Center for Disease Control and Prevention. That level could threaten herd immunity, the point at which “a sufficient proportion of a population is immune to an infectious disease… to make its spread from person to person unlikely.”
Dr. Tina Tan, an infectious disease specialist at Lurie Children’s Hospital in Chicago, says to be safe, vaccination rates should be at 95 percent. That sentiment is echoed by the World Health Organization.
“Here in Illinois unfortunately we still have medical as well as philosophical exemptions from vaccines,” Tan said. “So there are some parents who decide they don't want to vaccinate their children and take advantage of these exemptions."
The state’s overall adolescent measles vaccination rate is at 93.5 percent.
State law requires children in school to be vaccinated, but allows for two categories of exemption: medical and religious. Illinois law has a fairly low bar for showing the need for religious exemption.
The state requires “a written and signed statement from the parent or legal guardian detailing the objection” and the law states “the religious objection may be personal and need not be directed by the tenets of an established religious organization.”
The Illinois Department of Public Health has yet to comment.
Shannon Heffernan is a WBEZ reporter. Follow her @shannon_h. WBEZ digital producer Chris Hagan contributed to this story.