State, local data show different levels of COVID vaccine uptake in Tarrant County
Texas and Tarrant County officials are reporting two different numbers of county residents who have been vaccinated against COVID-19, meaning that officials at the various levels of government have different understandings of how many people in the county have been vaccinated.
According to the Texas Department of State Health Services (DSHS), there are 953,076 county residents who have received at least one dose of the COVID-19 vaccine as of Thursday.
But according to Tarrant County Public Health’s weekly update, published every Wednesday, there are 699,662 county residents who have gotten their first shot.
The two figures — a difference of more than 253,000 people — each paint a drastically different picture of vaccine uptake in the county.
The reporting issue stems from the complex system the state health department has for cleaning and verifying the information for vaccine distribution.
Lara Anton, spokesperson for the state health department, said the discrepancy appears to be happening because vaccine providers sometimes leave the county field blank or fill out the information incorrectly when entering data into ImmTrac2, the state’s vaccine immunization registry.
In Tarrant County, that’s an issue because there are multiple ZIP codes that cross county borders.
“When the county is missing, they try to do it by ZIP code,” Anton said. “With Tarrant County, there are a lot of ZIP codes that are either getting assigned unknown or going into Dallas or Denton, if it is a ZIP code that is bordering one of the other counties.”
But this misstep only affects the data that is given back to Tarrant County Public Health by the state.
Before the state publicly posts vaccine data on its dashboard, it goes through a second layer of data cleaning, Anton says, which uses an individual’s entire address to correctly detect the county of residence.
The data that’s going to Tarrant County Public Health, however, is cleaned using the ZIP codes alone.
“The more complete data is the state data that we post on our dashboard,” Anton said. “It goes through an extra layer of address matching and that’s why we’re able to better match an exact address to the data.”
The state’s COVID-19 vaccine data team is working on updating their code to address the issue with some Tarrant County ZIP codes, Anton said.
Brian Murnahan, a spokesperson for the county’s public health department, said in an email that the state had determined two potential reasons for the discrepancy.
“DSHS has identified an issue with the auxiliary lookup table which determines if a record is passed to a county. This issue is likely causing an under-reporting of vaccinated Tarrant County residents,” Murnahan wrote. “This is the larger reason for the discrepancy.”
Murnahan also said an extra layer of data cleaning was applied to vaccine data sent to TCPH, in contrast to the state’s explanation.
“This results in cleaner data being sent to TCPH compared to that being pulled for the DSHS dashboard,” Murnahan said.
To date, local health officials have relied on data reported on Tarrant County Public Health’s dashboard in conversations about vaccine uptake.
The difference underscores the challenge of understanding and creating public health policy and initiatives when local, state, and federal leaders are relying on different data.
Dr. Catherine Troisi, an infectious disease epidemiologist with UTHealth School of Public Health, said issues with data discrepancies often arise because of inefficient data communication systems and a smaller public health workforce than is needed to handle data systems during a pandemic. Those factors, coupled with chronic underfunding of public health programs, Troisi said, mean that data confusions are likely to come up.
“I don’t think we should be too hard on the practitioners because they’re dealing with a lot,” Troisi said. “If their only job were to collect vaccine data, that would be one thing, but they’re doing a lot of other things as well.”
Dr. Chris Lehmann, an expert in informatics, also said that years of underfunding has left health agencies unequipped for the flood of information that needs to be verified and tracked in real-time during a pandemic.
“This pandemic has made it abundantly clear that we don’t have the workforce that has the skills and the qualifications to the number-dredging necessary during a pandemic,” said Lehmann, who is the director of the Clinical Informatics Center at UT Southwestern Medical Center.
Comparing state and local data sources is complex for other reasons.
The state’s health department gauges the percent of a population that is vaccinated based on the population of people 12 and older, which is the population for which COVID-19 vaccines have been approved. The state’s data, and the state’s configuration for vaccine uptake, shows that about 55% of Tarrant County residents have begun the vaccination process.
But Tarrant County Public Health gauges vaccine uptake based on the entire population, no matter the age. TCPH’s update from Wednesday shows that 33% of residents have begun the vaccine process.
As communities try to gauge what proportion of their eligible population has been vaccinated, and how well protected they are against existing and future variants of the disease, differing data systems leave people with a confusing set of answers as to how many people have been vaccinated.
“For me as an individual, it’s important to know: Do I live in an area where I’ve achieved herd immunity?” Lehmann said.
This story was originally published July 10, 2021 at 5:30 AM.
