A Texas-sized Measles Epidemic Could be Coming

Researchers writing in PlosOne warn of the high potential for an epidemic of measles in Texas, where a sharp rise in non-medical exemptions to vaccination threaten to decrease overall vaccination effectiveness and create conditions for major outbreaks.

The study cited statistics from the Texas Department of State Health Services, which reported a 19-fold increase in children with nonmedical or “reasons of conscience” exemptions to school immunization laws since 2003. Current figures report almost 45,000 children with non-medical exemptions, which is double the number of exemptions in 2010. (See Fig 1.)

This is alarming, researchers say, because vaccine coverage for measles needs to be extremely high, “typically exceeding 90%–95%, in order to prevent a measles outbreak in a school or similar setting.”¹

But the recent statistics point to a “serious downward trend” in vaccination coverage to the point where there is a high risk that measles outbreaks will return. “Measles vaccination coverage in certain Texas counties is dangerously close to dropping below the 95% coverage rate necessary to ensure herd immunity and prevent measles outbreaks,” researchers wrote.

Figure 1.

Personal belief exemptions in Texas: K-12th grade students with nonmedical exemptions, Texas, 2003–2016. Original figure courtesy of The Immunization Partnership, 2016. Data from Texas Department of State Health Services, Annual Report of Immunization Status.
http://dx.doi.org/10.1371/journal.pmed.1002153.g002

In the event of an outbreak, researchers say each new primary case in a susceptible population would generate an average of 12-18 new cases of measles.

To combat this, Texas should enact state legislation similar to the laws that California recently passed to close loopholes allowing for non-medical exemptions to vaccines, researchers wrote. “This measure could prove to be lifesaving in the coming years. We now need to enact something similar for the children of Texas in order to prevent imminent deaths from measles and other vaccine-preventable childhood diseases.”