Population-Based Estimates of SARS-CoV-2 Seroprevalence in Houston, Texas as of September 2020

Abstract

Background In contrast to studies that relied on volunteers or convenience sampling, there are few population-based SARS-CoV-2 seroprevalence investigations and most were conducted early in the pandemic. The health department of the fourth largest city in the U.S. recognized that sound estimates of viral impact were needed to inform decision-making. Methods Adapting standardized disaster research methodology in September 2020, the city was divided into high and low strata based on RT-PCR positivity rates, and census block groups within each stratum were randomly selected with probability proportional to size, followed by random selection of households within each group. Using two immunoassays, the proportion of infected individuals was estimated for the city, as well as by positivity rate and by sociodemographic and other characteristics. The degree of under ascertainment of seroprevalence was estimated based on RT-PCR positive cases. Results Seroprevalence was estimated to be 14% with a near two-fold difference in areas with high (18%) versus low (10%) RT-PCR positivity rates and was four times higher compared to case-based surveillance data. Conclusions Seroprevalence was higher than previously reported and is greater than that estimated from RT-PCR data. Results will be used to inform public health decisions about testing, outreach, and vaccine rollout.

Ethnoracial Disparities in SARS-CoV-2 Seroprevalence in a Large Cohort of Individuals in Central North Carolina from April to December 2020

“…The conditional odds ratios we calculated assume that all other variables are held constant while estimating the effect of one demographic variable at a time. We found that Latinx individuals had the highest odds of SARS-CoV-2 seropositivity, followed by non-Latinx black individuals, corroborating observations within the United States, including urban centers as well as state-wide studies within and outside the American South ( 4 , 8 – 10 , 13 ). In nearby Virginia among outpatients as of August 2020, Hispanics were found to have about 6-fold increased seropositivity compared to white individuals ( 10 ).…”

“…In nearby Virginia among outpatients as of August 2020, Hispanics were found to have about 6-fold increased seropositivity compared to white individuals ( 10 ). Similarly, in Houston, Texas, by September 2020 as measured by representative population sampling, rates of seropositivity were about 3-fold higher among both non-Hispanic black and Hispanic individuals compared to non-Hispanic white individuals ( 8 ). Around that same time period, in our study, we found a 3- to 4-fold higher seropositivity among Latinx individuals compared to non-Latinx white individuals, which supports the previous findings in Texas and Virginia.…”

“…One study of asymptomatic inpatients and outpatients in central NC from 28 April to 19 June 2020 found an estimated SARS-CoV-2 seroprevalence of 0.7 to 0.8% over time, and another study of remnant clinical samples (3,817 from NC) from 27 July to 24 September 2020 found an estimated seroprevalence of 2.5 to 6.8% over this time period ( 6 , 7 ). Studies from other regions of the American South have also revealed variation in seroprevalence by demographic factors as well as self-reported disease ( 8 – 10 ). While overall seroprevalence estimates of a given study depend on sampling method, assay characteristics, geography, and temporal factors, seroprevalence studies provide information on the spread of COVID-19 that is missed by looking at the number of confirmed acute cases alone.…”

Temporal Variations in Seroprevalence of Severe Acute Respiratory Syndrome Coronavirus 2 Infections by Race and Ethnicity in Arkansas

“…Contrary to our expectations, SARS-CoV-2 spread uniformly across urban and rural areas of Arkansas. This finding differs from reports from the northeastern and northwestern US, and in southern cities such as Houston and New Orleans [ 31 , 32 ]. However, it is worth noting that Arkansas was home to a rural super-spreader event in March 2020 [ 33 ].…”

Economic and mental health impacts of multiple adverse events: Hurricane Harvey, other flooding events, and the COVID-19 pandemic

“…Low income and minority populations are more vulnerable to COVID-19 and flooding events. A population-based SARS-CoV-2 prevalence study conducted in Houston demonstrated the disproportionate impact of COVID-19 on minority populations ( Symanski et al, 2021 ). This study population, however, is mostly white.…”