Study findings from January 2021.
DFW COVID-19 Study Interim Findings – January 2021
As of January 28, 2021, there are over 25.6 million confirmed cases of COVID-19 in the United States and more than 463,000 cases in Dallas and Tarrant Counties.* It is estimated 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 North Texas to help develop strategies to improve public health. The study is recruiting in two ways: a community-based sample of adults from the two counties and a non-medical essential employee sample.
As of January 2021, over 18,500 individuals in Dallas and Tarrant Counties have participated by completing a survey and receiving free PCR and Antibody tests; this is a 50% increase from December 2020. Some key themes from the study are summarized below and a report of the interim findings follows. Additional reports will be published as study enrollment continues. The study is actively recruiting volunteers to participate with a focus on racial ethnic minorities and millennials.
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 6.2% for Dallas County and 7.0%. for Tarrant County. In the employee sample, there was active infection in 1.2% and prior infection in 4.4% 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 (over 92%) 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. More participants with any COVID infection reported eating inside a restaurant as compared to those with no history of infection (41% vs. 28%). Similarly, more participants with any infection attended small social gatherings with 5 or more people (33% vs. 23%).