Use of zip code based aggregate indicators to assess race disparities in COVID-19

Abstract

Objective: In the first six months of the pandemic, information on race and ethnicity was missing for half of the US COVID-19 cases. Combining case ascertainment with census-based zip code indicators may identify COVID-19 race-ethnicity disparities in the absence of individual-level data. Design: Ecological retrospective study for the period March-July 2020. Setting: Population-based investigation, Allegheny County, Pennsylvania. Participants: All COVID-19 cases, adjusted for zip code area population, in the early period of the pandemic. Main Outcome Measures: Monthly COVID-19 incidence and requests for human services by zip code level indicators of race-ethnicity and poverty. Results: In the early period of the pandemic, COVID-19 incidence was higher in zip codes with a greater proportion of racial and ethnic minorities. Zip codes with the highest quartile of minority residents (>25.1% of population) had a COVID-19 incidence of 60.1 (95% CI: 51.7-68.5) per 10,000 in this period; zip codes with the lowest quartile of minority residents (<6.3%) had an incidence of 31.3 (95% CI: 14.4-48.2). Requests for human services during this period (volume of 211 calls and county services) confirm these disparities. Conclusion: Use of census-defined raceethnicity proportions by zip code offers a way to identify disparities when individual race-ethnicity data are unavailable.