The COVID-19 pandemic caused by SARS-CoV-2 has resulted in millions of deaths globally. Rapid vaccine development was a significant achievement, but effective vaccine delivery is crucial to ending the pandemic. Logistical challenges and supply chain issues hampered early vaccination efforts, especially in the U.S., where fewer doses were administered compared to the U.K. by February 2021. Racial and ethnic minorities face a disproportionately high risk of severe COVID-19 outcomes, yet vaccine programs initially prioritized healthcare workers, older adults, and those with comorbidities, without explicit consideration of race or ethnicity. Vaccine hesitancy, stemming from mistrust of the medical system due to historical injustices and discrimination, presents a significant barrier to uptake in these communities. The U.S. and U.K., both with diverse populations differentially affected by COVID-19, present a valuable comparative case study. The U.K.'s centralized National Health Service contrasts with the U.S.'s fragmented state and local health authorities, which impacted data collection and vaccine rollout. While racial and ethnic disparities in vaccine uptake have been reported, comprehensive data from large, community-based samples, particularly in the U.S., were lacking. This study aimed to assess the initial impact of vaccination programs by examining country-specific variations in racial and ethnic disparities in vaccine willingness and uptake using a smartphone-based data collection tool.

Existing literature highlights the disproportionate impact of COVID-19 on racial and ethnic minorities, showing increased risk of infection, complications, and death. Studies have demonstrated lower vaccine uptake among these groups, often attributed to vaccine hesitancy rooted in mistrust of the medical system due to historical and ongoing discrimination. Differences in vaccine delivery systems between the U.S. and U.K. have been noted, with the U.K.'s centralized system contrasting with the more fragmented approach in the U.S. Previous studies, though often smaller in scale, indicated increased vaccine hesitancy among minority groups. However, large-scale studies comparing vaccine hesitancy and uptake in these diverse populations across countries were limited. This work builds upon previous research by providing a comprehensive comparison, leveraging the unique dataset of the COVID Symptom Study.

This study employed a prospective, population-based cohort design using data from the COVID Symptom Study (CSS) smartphone application. The CSS application, used in both the U.S. and U.K., collected data from March 2020 to February 2021, with a focus on vaccine willingness and uptake starting in December 2020 (U.K.) and January 2021 (U.S.). Participants, aged 18 and older, provided informed consent for research purposes. Ethical approvals were obtained from relevant Institutional Review Boards. The study population included over 4 million participants, with a final analytic cohort of 1,341,682 individuals after exclusions. Racial and ethnic identity was self-reported using standardized categories from the NIH (U.S.) and Office for National Statistics (U.K.). Other covariates included age, sex, comorbidities, smoking status, BMI, frontline healthcare worker status, geographic region (U.S.) or country (U.K.), and community-level socioeconomic factors. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for vaccine hesitancy and uptake, adjusted for relevant covariates. Inverse probability weighting (IPW) analyses were conducted to address potential undersampling. Stratified analyses were performed to investigate differences among subgroups (frontline healthcare workers, general community, varying levels of income and education).

Among 1,228,638 participants who answered the vaccine willingness question, 91% of U.S. and 95% of U.K. participants reported willingness to receive a vaccine. In the U.S., compared to white participants, vaccine hesitancy was significantly higher among Black (OR 3.84, 95% CI: 3.51-4.21), Hispanic (OR 1.69, 95% CI: 1.53-1.86), Asian (OR 1.22, 95% CI: 1.03-1.38), and those reporting other or more than one race (OR 2.14, 95% CI: 1.82-2.52). Similar levels of hesitancy were observed among racial and ethnic minorities in the U.K. Reasons for hesitancy commonly cited included concerns about long-term side effects and adverse reactions; Black and Hispanic participants also reported a lack of knowledge about the vaccine at higher rates. In the U.S., Black participants had significantly lower vaccine uptake than white participants (OR 0.71, 95% CI: 0.64-0.79), even after adjusting for covariates. This difference persisted among vaccine-willing participants. In contrast, no significant racial or ethnic disparities in vaccine uptake were observed in the U.K. sample. This disparity in vaccine uptake between Black participants in the U.S. and the U.K. was statistically significant (Pheterogeneity < 0.001). No consistent differences were observed in self-reported injection-site reactions by race or ethnicity. Subgroup analyses revealed that lower vaccine uptake among Black U.S. participants persisted across various socioeconomic and occupational groups.

This study confirmed increased COVID-19 vaccine hesitancy among racial and ethnic minority groups in both the U.S. and U.K., particularly among Black and Hispanic participants. The significant disparity in vaccine uptake observed among Black participants in the U.S., but not in the U.K., highlights the potential role of access disparities in addition to hesitancy. The higher hesitancy among U.S. Black participants was not fully explained by lower socioeconomic status, suggesting that factors beyond individual-level characteristics contribute to these differences. The findings underscore the need for targeted education campaigns delivered by trusted sources to address vaccine hesitancy in minority communities. Differences in healthcare systems, specifically the more centralized structure in the U.K. versus the fragmented U.S. system, may explain the observed differences in uptake. The study’s findings have implications for policies aimed at ensuring equitable vaccine distribution and addressing systemic inequalities that influence health outcomes.

This large-scale study revealed higher COVID-19 vaccine hesitancy among racial and ethnic minorities in both the U.S. and U.K., particularly in Black and Hispanic populations. A significant disparity in vaccine uptake was observed for Black U.S. participants, even among the vaccine-willing, highlighting access inequalities. The contrasting experiences of the U.S. and U.K. highlight the importance of addressing systemic health inequities to achieve equitable vaccine distribution and broader population immunity. Future research should investigate the underlying mechanisms of these disparities and develop effective strategies to overcome barriers to vaccine access and uptake in minority communities.

This study relied on self-reported data, which may be subject to bias. The study population, while large and diverse, was not a random sample of the U.S. and U.K. populations and might be enriched for individuals more receptive to vaccines. The use of a smartphone application for data collection may have introduced bias due to differential access to technology across socioeconomic groups. While extensive demographic and health information was collected, some individual-level data limitations existed, such as limited detail on racial and ethnic self-identification, and community-level measures of education and income.