Texas CARES project offers insights into COVID-19 antibody response among Texans

The Texas Coronavirus Response Survey (Texas CARES) provides improved understanding of how COVID-19 antibody response plays out across our state, in different communities and populations as well as over time.

Texas CARES is not only one of the largest longitudinal COVID-19 seroprevalence surveys in the world, and likely the largest survey of children and adolescents over time, it can differentiate between a person’s antibodies derived from the vaccine versus natural infection or if the person has both vaccine and COVID-19 infection-derived antibodies. Seroprevalence refers to the percentage of individuals in a population who have antibodies to an infectious agent.

Texas CARES is managed by a collaborative team from The University of Texas Health Science Center at Houston (UTHealth Houston) School of Public Health, in partnership with the Texas Department of State Health Services (DSHS), Clinical Pathology Laboratories (CPL), and The University of Texas System. Texas CARES is funded by Texas DSHS.

Key goals of Texas CARES

• To estimate how many people in Texas have been infected with, and recovered from, SARS-CoV-2.
• To estimate how many people have been vaccinated for SARS-CoV-2 and develop antibodies.
• To test how long COVID-19 antibodies last in someone's system.
• To identify the characteristics of people who develop COVID-19 antibodies.
• To identify the characteristics of people who do not develop COVID-19 antibodies following exposure to the virus or vaccination.

Data collected through Texas CARES continues to provide answers to important questions about antibody response to COVID-19 in the Texas population. These antibodies can arise from a naturally occurring infection or from the vaccine.

The program provides an informative way for participants to track their antibody levels in response to COVID-19 infection and/or vaccination over time.

Who participates in Texas CARES?

Texas CARES enrolled Texans between the ages of five and 90 years of age. Participants were invited for three blood draws and COVID-19 antibody tests over a period of six to eight months. Of the 89,723 people from 234 counties across the state participating in Texas CARES, 67.2% are female; 20.8% are 20-39 years of age, and 14.8% are Hispanic.

Principal Investigator Eric Boerwinkle, Ph.D., Dean of the UTHealth School of Public Health, explains, “Our School of Public Health’s vision of health without boundaries is not about geography. Both Texas CARES and our School of Public Health span boundaries of race and ethnicity — and share the goal to meet the needs of the underrepresented and the underserved.”

As of March 28, there were 42,169 Texas CARES participants who completed antibody tests at all three timepoints. More will become eligible for their third antibody test throughout April.

As the pandemic has evolved, adds Dr. Boerwinkle, “the goals and impact of Texas CARES have also evolved. Our initial goal was to estimate seroprevalence across the state and over time, and it has now shifted to our ability to distinguish antibodies from the vaccine, antibodies from the virus and the predictors of breakthrough infections. In addition, we know there will be another pandemic and our goal is to ensure Texas is prepared to provide important insights into preparedness and response, which is why we are pleased that the state has established the Texas Epidemic Public Health Institute (TEPHI) as a new agency keeping Texans safe and the Texas economy strong.”

Overview of key findings

As of March 28, 95% of the Texas population with SARS-CoV-2 antibodies presumably benefit from some degree of protection from COVID-19. The level of protection from naturally acquired antibodies compared to antibodies for vaccination is still unknown.

Antibody levels to a natural infection peak in about 120 days after infection and then decrease, but remain detectable, after 275 to longer than 500 days. Data also illustrates that fully vaccinated participants show significantly higher antibody levels than those with a natural infection only. These data suggest that vaccination may provide the highest level of protection, even for those who have had prior COVID-19 infections and developed antibodies.

“Participants shared with us that one benefit of testing over time is that they are able to track their antibody levels of both the N-test (viral induced) and the S-test (vaccine and viral induced) in response to infection (known or unknown), as well as vaccination and boosters,” explains Co-Investigator Sarah E. Messiah Ph.D., MPH, director of the Center for Pediatric Population Health at UTHealth School of Public Health.

“The survey will provide a better understanding of the COVID-19 antibody response, and the knowledge may help inform local and state policies,” she says.

“There is still a lot we don’t know about COVID-19 antibodies,” says Co-Investigator Ashraf Yaseen, Ph.D., Assistant Professor of Data Science at the UTHealth School of Public Health. “People with antibodies to COVID-19 from a previous infection may have an immune response to a future infection, but we don’t have enough evidence to know who may be protected from a second infection, and how often this happens.”

Findings in children

There are currently 4,004 children and adolescents ages 5-19 participating in the Texas CARES project.

More than a third of children have antibodies to the virus, and of those, 54% reported never having had symptoms.

COVID-19 antibodies from infection persist at least six months in children, but the level of protection granted by these antibodies remains unknown.

UTHealth School of Public Health team

Lead Co-Investigator is Stacia M. DeSantis. Other Co-Investigators are Michael D. Swartz, Melissa A. Valerio, Steven H. Kelder, W. Bill Kohl, and Luis Leon Novelo. The Research Coordinator is Lindsay Padilla, and Project Managers are Camille Breaux and Jessica A. Ross. Staff are Michael Gonzalez, Leqing Wu, and Yashar Talebi.

The Texas Epidemic Public Health Institute (TEPHI) is a network of public health professionals and resources that ensure the state is at the forefront of pandemic readiness and response.

TEPHI’s new certificate program is offered by The UTHealth School of Public Health, the largest school of public health in the state with six campuses. The certificate in Pandemic Preparedness and Response is an online, self-paced program that covers fundamentals of pandemic preparedness and response. Information can be found on tephi.texas.gov.

More information on Texas CARES may be found on sph.uth.edu/projects/texascares.