Discussion

This study was a retrospective chart review using a stratified sampling method of Delta and Omicron variant infected patients who presented to an emergency department at an academic, safety-net hospital between September 2021 and January 2022. Analyses revealed worse overall disease outcomes and higher treatment requirements for patients infected with the Delta variant compared to propensity score-matched patients infected with the Omicron variant. Disease burden continued to be higher for Delta patients after stratifying by vaccination status. A multivariable model identified medical comorbidities such as kidney, liver, and respiratory disease along with cancer as predictors of more severe disease. Further, 2 doses of COVID-19 vaccine were reported to be protective against severe disease.

This study oversampled Black patients consistent with overall hospital demographics. As race is a social construct that is not representative of biological differences, it is important to analyze the ways structural racism has impacted the Black community throughout the COVID-19 pandemic. In New York City, the first epicenter of the pandemic, a higher population density of Black residents was the strongest predictor of neighborhood COVID-19 test positivity, even after controlling for socioeconomic status, comorbidities, and age. ^{Reference DiMaggio, Klein, Berry and Frangos16} Later analyses of possible contributing factors reported that Blacks in New York City comprise a large sector of frontline jobs, increasing exposure to the virus. ^{Reference Arasteh17} Another study found a decrease in the death rate in Black communities with higher unemployment, possibly due to ability to shelter in place. ^{Reference Boserup, McKenney and Elkbuli18} Racial/ethnic minorities as a whole are more likely to have positive COVID-19 test results and require admission to the hospital and ICU in the United States. ^{Reference Mackey, Ayers and Kondo12,Reference Tai, Shah, Doubeni, Sia and Wieland13,Reference Boserup, McKenney and Elkbuli18,Reference Khanijahani, Iezadi, Gholipour, Azami-Aghdash and Naghibi19} This study was underpowered to detect inequities between racial groups, hence it is not surprising that race was not predictive of disease severity in the multivariable model. The study outcomes, however, largely represent a Black, urban patient population with unique vulnerabilities to the effects of COVID-19.

The COVID-19 literature has demonstrated that vaccination status plays a role in illness severity. Given the lack of standardized vaccine registry in the United States, the current study was not powered to detect a difference in disease severity by vaccination status. This study did, however, detect a trend toward protection from severe disease, regardless of variant, in patients who received 2 doses of the COVID-19 vaccine. Further, patients with 3 vaccine doses trended toward more mild-moderate disease compared to their unvaccinated counterparts. The study population who had received 3 doses was small (n = 42) and may represent a higher-risk group who was eligible for booster doses before the general public. Additionally, Black Americans have had the slowest uptake of the primary vaccine series and the second slowest uptake of the booster dose. ^{Reference Baker, Phillips, Faherty, Ringel and Kranz20} Black participants in a survey conducted in the United States reported being the least likely racial/ethnic group to vaccinate themselves or those in their care, due to mistrust and perception of risk and severity. ^{Reference Viswanath, Bekalu, Dhawan, Pinnamaneni, Lang and McLoud21} A large study conducted across American hospitals reported that 3 doses were necessary to achieve the same protection against the Omicron variant as 2 doses provided against the Delta variant. ^{Reference Lauring, Tenforde and Chappell22} The authors note that in the unvaccinated population, the Delta variant drove higher disease severity. Therefore, the increased disease severity in the Delta variant population may be driven by higher proportion of unvaccinated and undervaccinated individuals. Furthermore, the effect of Delta on disease severity existed after controlling for vaccination status.

Disease severity was further compounded by medical comorbidities, which also display unsettling patterns of racial inequity. Patients with preexisting kidney disease and hypertension were roughly 2 and 3 times as likely to develop mild-moderate disease, respectively. Effects were greater in the severe disease cohort. Patients with kidney disease (aOR: 4.26), cancer (aOR: 6.9), respiratory disease (aOR: 5.78), and/or liver disease (aOR: 3.91) were at a substantially higher risk of suffering from severe disease outcomes, like ICU admission or requiring high-flow oxygen. The health inequity literature acknowledges several important trends in the COVID-19 pandemic. In a Black, urban population, participants were more likely to have hypertension, diabetes, and a higher number of comorbidities overall, regardless of age. ^{Reference Arasteh17} Black patients are also over-represented in the asthmatic population, leading to more hospitalization secondary to COVID-19. ^{Reference Chhiba, Patel and Vu23} Despite reported differences in baseline comorbidity rates, Black participants are underrepresented in COVID-19 prevention strategy trials. ^{Reference Xiao, Vaidya, Liu, Chang, Xia and Sex24} There is, however, equal representation of Black Americans in COVID-19 treatment trials.

This study has several strengths that add to the existing literature. Namely, a lower socioeconomic status, Black, and urban population were oversampled. Though insurance information was not readily available for all participants, it is reasonable to extrapolate socioeconomic status given typical hospital demographics, especially in the Emergency Department. Therefore, this study captures a particularly vulnerable population. The study time period was carefully selected to include the peak of both Delta and Omicron waves at the institution. The trends presented here regarding comorbidities, vaccination status, and disease outcomes inform the national discourse on how to protect a disproportionately affected sector of the United States population in the setting of another potential surge.

This study is limited in its generalizability. It was conducted at a single academic center at a cross-section in time. Vaccination status was based on patient report and provider documentation, which limits reliability and contributes to missing data. To control variables, this study evaluated only patients who presented to the emergency department and may be more symptomatic with greater numbers of comorbidities than other patient populations. However, it is the anecdotal observation of the authors during chart review that the ED was being used inappropriately by patients as an asymptomatic testing center at this stage of the pandemic. It has also been reported that Black patients are more likely to get COVID-19 testing in the ED or inpatient than in the ambulatory setting. ^{Reference Azar, Shen and Romanelli25}

Overall, these data support reports of higher morbidity due to the COVID-19 pandemic in minority populations and those suffering from chronic medical conditions. Disease severity was worse in the Delta variant cohort regardless of vaccination status. Illness severity was further mediated by medical comorbidities. This work serves to inform public health efforts to serve especially vulnerable patient populations with multiple medical comorbidities, such as the low socioeconomic status, predominantly Black urban population described here.