Quantifying Inequities in COVID-19 Vaccine Distribution Over Time by social vulnerability, race and ethnicity, and location: A Population-Level Analysis in St. Louis and Kansas City, Missouri
Authors: Mody Aaloke , Bradley Cory , Redkar Salil , Fox Branson , Eshun-Wilson Ingrid , Hlatshwayo Matifadza G. , Trolard Anne , Tram Khai Hoan , Filiatreau Lindsey M. , Thomas Franda , Haslam Matt , Turabelidze George , Sanders-Thompson Vetta , Powderly William G. , Geng Elvin H. 
Published: June 2022

BACKGROUND

Equity in vaccination coverage is a cornerstone to a successful public health response to COVID-19. To deepen understand of the extent to which vaccination coverage compared to initial strategies for equitable vaccination, we explore primary vaccine series and booster rollout over time and by race/ethnicity, social vulnerability, and geography.

METHODS AND FINDINGS

We analyzed data from the Missouri State Department of Health and Senior Services on all COVID-19 vaccinations administered across 7 counties in the St. Louis region and 4 counties in the Kansas City Region. We compared rates of receiving the primary COVID-19 vaccine series and boosters relative to time, race/ethnicity, zip code-level social vulnerability index (SVI), vaccine location type, and COVID-19 disease burden. We adapted a well-established tool for measuring inequity—the Lorenz curve—to quantify inequities in COVID-19 vaccination relative to these key metrics. Between 12/15/2020 and 2/15/2022, 1,762,508 individuals completed the primary series and 871,896 had received a booster. During early phases of the primary series rollout, Black and Hispanic individuals from high SVI zip codes were vaccinated at less than half the rate of White individuals, but rates increased over time until they were higher than rates in White individuals after June 2021; Asian individuals maintained high levels of vaccination throughout. Increasing vaccination rates in Black and Hispanic communities corresponded with periods when more vaccinations were offered at small community-based sites such as pharmacies rather than larger health systems and mass vaccination sites. Using Lorenz curves, zip codes in the quartile with the lowest rates of primary series completion accounted for 19.3%, 18.1%, 10.8%, and 8.8% of vaccinations but represented 25% of either the total population, cases, deaths, or population-level SVI, respectively. When tracking Gini coefficients, these disparities were greatest earlier during rollout, but improvements were slow and modest and vaccine disparities remained across all metrics even after one year. Patterns of disparities for boosters were similar but often of much greater magnitude during rollout in Fall 2021. Study limitations include inherent limitations in vaccine registry dataset such as missing and misclassified race/ethnicity and zip code variables and potential changes in zip code population sizes since census enumeration.

CONCLUSIONS

Racial inequity in the initial COVID-19 vaccination and booster rollout in two large U.S. metropolitan areas were apparent across racial/ethnic communities, across levels of social vulnerability, over time, and across types of vaccination administration sites. Disparities in receipt of the primary vaccine series attenuated over time during a period in which sites of vaccination administration diversified, but were recapitulated during booster rollout. These findings highlight how public health strategies from the outset must directly target these deeply embedded structural and systemic determinants of disparities and track equity metrics over time to avoid perpetuating inequities in health care access.

AUTHOR SUMMARY

Why Was This Study Done?

Equitable vaccine strategies are critical for the public health response to COVID-19, but there is limited understanding of how vaccination campaigns compared to different metrics for equity.

Many initial approaches to vaccine allocation sought to acknowledge the known disparities in exposure risk, disease burden, needs, and access by formally considering social vulnerability or race/ethnicity in plans to prioritize vaccinations, but there is limited empirical evaluation of how actual primary vaccine series and subsequent booster efforts aligned with the initial goals set out for equity.

We quantify COVID-19 vaccine-related inequities in receipt of the primary vaccine series and booster across key equity metrics including race/ethnicity, social vulnerability, location, and time using a novel application of Lorenz curves and Gini coefficients—tools from economics to measure inequalities—in the St. Louis and Kansas City regions of Missouri.

What Did the Researchers Do and Find?

We analyzed data from the Missouri State Department of Health and Senior Services on all COVID-19 vaccinations administered in the St. Louis region and Kansas City Regions. We compared rates of receiving the primary COVID-19 vaccine series and boosters relative to time, race/ethnicity, zip code-level social vulnerability index (SVI), vaccine location type, and COVID-19 disease burden. We adapted Lorenz curves and Gini coefficients to quantify the inequities in COVID-19 vaccination relative to these key metrics and examined how they changed over time.

Black and Hispanic individuals from high SVI zip codes completed the primary series at less than half the rate of White individuals during early phases of the primary series rollout, but surpassed rates in White individuals after June 2021. These relative increases in primary series completion rates in Black and Hispanic communities corresponded to periods when vaccinations became more available at small community-based sites.

Lorenz curves demonstrated that zip codes in the quartile with the lowest rates of primary series completion accounted for 19.3%, 18.1%, 10.8%, and 8.8% of vaccinations but represented 25% of either the total population, cases, deaths, or population-level SVI, respectively. Tracking Gini coefficients over time demonstrated that these disparities were greatest earlier during rollout, but only improved slowly and modestly over time.

Patterns of disparities for boosters were similar but often of much greater magnitude that those seen with completion of the primary vaccine series. patterns of disparities were similar but often of greater magnitude during booster rollout in Fall 2021.

What Do These Findings Mean?

Vaccination coverage for both the primary series and boosters demonstrated substantial disparities across race/ethnicity, levels of social vulnerability, types of vaccine administration sites, and over time.

Despite well-documented inequities for COVID-19 and need for equitable vaccine approaches, the strategies employed did not overcome deeply entrenched systemic inequities in health care and society.

Public health strategies must proactively target these deeply embedded structural determinants of disparities from the outset and should systematically track equity metrics over time to avoid perpetuating inequities in health care access.