Study findings from March 2021.
DFW COVID-19 Study Interim Findings – March 2021
As of March 26, 2021, there are over 30 million confirmed cases of COVID-19 in the United States and more than 539,000 cases in Dallas and Tarrant Counties.* Centers for Disease Control & Prevention estimates that 40% of people who have SARS-CoV2, the virus that causes COVID-19, are asymptomatic (no signs or symptoms) and that asymptomatic individuals can spread the virus.** With testing and contact tracing being limited early in the pandemic, it is difficult to determine how widespread COVID-19 has been in the local community.
In response to these factors, UT Southwestern Medical Center and Texas Health Resources launched the DFW COVID-19 Prevalence Study to understand how many people, by demographic groups, are or have been infected in Dallas and Tarrant Counties to help develop strategies to improve public health. The study recruited in two ways: a community-based sample of adults from the two counties and a non-medical essential employee sample.
Over 21,300 individuals in Dallas and Tarrant Counties participated by completing a survey and receiving free tests to check for active infection (PCR) and past infection (Antibody). Some key study findings are summarized below and an interim report follows. Additional reports will be published as study follow-up continues. The study completed recruitment in February 2021 and is now conducting a follow-up survey and testing to describe long COVID symptoms (lasting more than 4 weeks).
Active vs. Prior Infection
The COVID virus can persist on PCR tests in some people despite their no longer being contagious. In our study, one-third of people were both PCR-positive and Antibody-positive, which means they have had virus long enough to develop antibodies and their infections are likely resolved. Based on this finding, we have presented the data as three groups: (1) those with active infections (PCR+, Antibody -), (2) those with prior or resolved infections (Antibody+), and (3) those who have not been infected (PCR -, Antibody -). This provides a more accurate picture of active infection rates.
In the community sample, active infection was found in 1.8% and 2.6% of Dallas and Tarrant County participants, respectively. Prior infection was found in 7.2% for Dallas County and 8.5%. for Tarrant County. In the employee sample, there was active infection in 1.1% and prior infection in 5.2% of participants.
Like other research, the study found that COVID infection is more common in racial/ethnic minorities and younger individuals. Hispanics had the highest proportion of active (4.4%) and prior (11.0%) infections, followed by African Americans who had active infection in 3.1% and prior infection in 9.0% of participants. In comparison, Non-Hispanic Asians had the lowest proportions, with active infection in 0.7% and prior infection in 4.4% of participants. Among different age groups, individuals who were 18-24 years old had the highest proportion of active (3.8%) and prior (7.8%) infections.
Despite differences in COVID infection across communities, these data highlight that we are well short of the 70-85% infected rate necessary to achieve herd immunity across all populations and the importance of distributing the COVID vaccine to protect the community.
The study examined behaviors and beliefs of participants as potential drivers of the observed demographic disparities. We found that mask-wearing was universally high (93%) among all participants. However, the study found significant differences in two behaviors between those with any COVID infection (active or prior) and those with no infection. Participants with any COVID infection were 1.5-2 times more likely to have attended small social gatherings or ate inside a restaurant suggesting these behaviors may have increased risk of infection. Data support public policies restricting indoor dining and small gatherings when infection rates are surging.
As the vaccine distribution began, the study surveyed participants to determine how many people had been vaccinated and how many planned to get vaccinated once it became available. While most were planning to vaccinate, a notable 25% of participants expressed vaccine hesitancy, saying they were uncertain or unlikely to take the vaccine when offered. These data mirror national estimates and we are partnering with community- and faith-based organizations to plan programs addressing hesitancy in DFW.
Though recruitment is over, we are partnering with other researchers to continue the study in several ways. We will issue additional reports as more data becomes available. In May, we will release data on the demographic, behavioral, and other factors that might be driving the racial, ethnic, and socioeconomic differences. Mid-Spring we will begin retesting COVID-positive participants to determine how long antibodies stay in the system. The Study’s Community Advisory Board is helping to shape communication and optimizations to improve vaccine implementation to prevent disparities in vaccine uptake and access.
The Study Team would like to especially thank the Study’s Community Advisory Board for their invaluable feedback and input, as well as the numerous government officials and community partners who tirelessly promoted the Study and helped to recruit over 21,000 participants. Support for this research was generously funded by community philanthropy, including Lyda Hill Philanthropies, W.W. Caruth, Jr. Fund at Communities Foundation of Texas, Harry S. Moss Heart Trust, Bank of America, N.A., Trustee, and many others.