The results were shared during a briefing on Monday hosted by Mayor Sylvester Turner detailing the status of the city's antibody testing initiative.
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Phase one of the program kicked off in September in which 420 homes were randomly selected and all members of each household were asked to answer questions and provide a blood sample.
Loren Hopkins, the Houston Health Department's chief environmental science officer, said participation exceeded the city's expectations, calling it "amazing." She adds 678 people provided blood samples.
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"Our results show that an estimated 13.5% of Houstonians, which is approximately 250,000 people, had been infected with COVID-19 by September," explained Hopkins.
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Data from the survey, which was an ongoing collaboration between the health department, Baylor College of Medicine and Rice University, showed an estimated 13.5% of Houstonians (approximately 250,000 people) previously had COVID-19 by Sep. 19.
The city says at that time, only 57,000 infections were identified by traditional viral testing.
The results also showed that a higher proportion of people with antibodies lived in high positivity rate areas (18%) of the city than those who lived in low positivity rate areas (10%).
Plus, the city says more women (17%) than men (10%) had antibodies, more Hispanics (18%) and Blacks (15%) had antibodies than non-Hispanic Whites (5%), and more people under 40 years of age (17%) than 40 and older (9%) had COVID-19 antibodies in their blood.
Survey teams will conduct phase two of the survey in January when people who participated in phase one will be re-tested to measure the number of antibodies remaining in their blood. Teams will also visit 420 new random Houston homes.
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Only homes approached by the project's teams are eligible to participate, and participation is voluntary. The teams will be identifiable by their "Better. Together." shirts.
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For more information about the antibody survey, visit the city of Houston's website.
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