Risk of measles outbreak in Tarrant County increases as vaccinations fall in kids

Because there are fewer Tarrant County children who have received the measles, mumps, and rubella vaccine in the last year, the county is at an increased risk of a measles outbreak like the one spreading in Columbus, Ohio, epidemiology experts said.

“Measles is sort of the canary in the coal mine,” said Dr. William Moss, the director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health. “It’s probably the most contagious of vaccine preventable diseases.”

The outbreak in Ohio has infected 85 people, according to data from the Columbus Department of Public Health. Almost all of the cases are in unvaccinated children, and at least 36 people have been hospitalized.

Epidemiology experts said the combination of decreased measles vaccination rates throughout the world and in the United States, including in Fort Worth, and the ability of the virus to spread easily puts North Texas at an increased risk of an outbreak.

“There are many communities just like Columbus, throughout the United States, including perhaps Fort Worth, where there are large enough numbers of susceptible individuals, whether they’re children or adults, to fuel a measles outbreak,” Moss said.

Those susceptible individuals are people who haven’t been fully vaccinated with at least two doses of the measles, mumps, and rubella vaccine. As cases of the virus increase globally, the risk locally will increase, he said.

How measles outbreaks start

Measles was declared eradicated in the U.S. in 2000, thanks to the wide availability and effectiveness of the MMR vaccine.

Because measles is not spreading within communities or throughout the U.S., virtually every known measles outbreak in recent history has happened when someone traveled abroad and brought the virus back to the U.S., where the traveler has transmitted the virus to susceptible, unvaccinated communities. Outbreaks typically occur when a cluster of unvaccinated people live, work, or play in the same community, and then a traveler introduces the virus to that community, said Diana Cervantes, an assistant professor at the University of North Texas Health Science Center.

That’s what happened in Tarrant County in 2013, when a man traveled abroad and then visited the Eagle Mountain International Church in Newark, the Tarrant County Public Health Department said at the time. The virus is believed to have spread from the man to a day care within the church, where some of the children were not up-to-date on their MMR vaccines, said Cervantes, who previously investigated outbreaks for Tarrant County Public Health.

That outbreak ultimately spread to 21 people, none of whom were hospitalized.

Measles vaccination rates in Tarrant County

Almost a decade later, the risk of such an outbreak in Tarrant County has, in some ways, increased, as there are more children who have not received their required MMR vaccines now compared to before the start of the COVID-19 pandemic. Across the Fort Worth school district, the county’s largest, just 85% of kindergartners had received the MMR vaccine in the last school year, according to data from the state health department.

But even this data can only indicate some of the risk, Moss said.

“What that overall average number doesn’t capture is the more fine scale clustering of susceptible individuals, which tends to happen because parents who decline to vaccinate their children, for example, often live together in the same communities,” Moss said. So even though the districtwide vaccination rate is 85%, there might be campuses with lower or higher vaccination rates.

A key factor in whether more Tarrant County kids will get up-to-date on their required immunizations is whether the decline was caused by a lack of access during the pandemic or whether it was caused by a decrease in trust in vaccines generally.

A recent public opinion poll from the Kaiser Family Foundation found that nearly one in three parents surveyed were opposed to their childhood vaccines like the MMR being required in schools.

If the dip in vaccinations is driven largely by decreasing trust in MMR vaccines and other immunizations, it could take a longer time to protect vulnerable kids and leave the county at greater risk of an outbreak, Cervantes said.

“You’re going to start seeing these pockets of people who are undervaccinated, and it just takes a matter of one introduction to begin an outbreak,” Cervantes said.

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