Ensuring racial and ethnic diversity in clinical trials for development of COVID-19 vaccines is particularly important since COVID-19 has taken a heavy disproportionate toll on people of color, and people of color, particularly Black adults, historically have had lower vaccination rates and express more concerns about getting a COVID-19 vaccine compared to their White counterparts. Diversity within clinical trials for a COVID-19 vaccine helps ensure safety and effectiveness across populations and may increase confidence in getting the vaccine among people of color. Historically, people of color have been underrepresented in clinical trials. There have been recent efforts to increase racial diversity within clinical trials and specific efforts to increase diversity within the trials associated with development of COVID-19 vaccines. With two COVID-19 vaccines now authorized in the U.S. (the Pfizer-BioNTech and Moderna vaccines), we review why racial diversity within COVID-19 vaccine clinical trials is important, discuss the barriers to participation in clinical trials among people of color, and examine the racial/ethnic composition of clinical trial participants for the Pfizer-BioNTech and Moderna vaccines.

Why is it important to have diversity within the COVID-19 vaccine trials?

Diverse racial/ethnic representation in COVID-19 vaccine trials is important because drugs and vaccines can differentially affect groups reflecting variation in underlying experiences and environmental exposure. Clinical trials are research studies that determine whether medical products like medicines, vaccines, or devices are safe and effective. It important for participants in clinical trials to represent the patients that will be using the medical products since responses may vary across patient groups. In general, to be representative, vaccine trials should enroll people of color in percentages similar to their representation in the population. However, since people of color have been disproportionately affected by COVID-19 pandemic, scientists, including Dr. Fauci, have indicated that the COVID-19 vaccine trials should overrepresent people of color compared to their population share.

Why are people of color underrepresented in clinical trials?

Access barriers, lack of information, and historic and ongoing racism and discrimination contribute to underrepresentation of people of color in clinical trials. People of color face an array of structural access-related barriers to participating in trials. For example, fewer clinical trials are available through under-resourced hospital systems where people of color are more likely to receive care, and people of color may be less likely to be eligible to participate in trials if being uninsured or having co-morbidities excludes individuals from participation. Other access challenges, such as prohibitive distance to trial sites for people with limited transportation options, limited flexibility in work and caregiving schedules, and lack of access to technology for monitoring that may be required as part of the trial also may increase barriers to participation among people of color. Beyond these challenges, lack of awareness and information may limit participation. For example, some research suggests that physicians are less likely to discuss clinical trials with patients of color. Further, enrollment efforts may not effectively reach people of color if they are not culturally appropriate and do not address differences in language and health literacy. Moreover, the medical system’s historic abuse and mistreatment of people of color, including but not limited to the infamous Tuskegee syphilis experiment, as well as ongoing racism and discrimination in health care today may contribute to less willingness among people of color to participate in clinical trials.

What steps are being taken to increase racial diversity within clinical trials?

There have been ongoing efforts to increase diversity in clinical trials broadly and specific to development of COVID-19 vaccines. The Federal Drug Administration (FDA) is engaged in a range of efforts to encourage greater diversity in clinical trials, including creating a public-facing education and outreach campaign and working with varied stakeholders. It also developed recommendations to industry and agency staff on how to collect race and ethnicity data in clinical trials. The National Institutes of Health (NIH) has longstanding guidelines on the inclusion of women and minorities as subjects in clinical research. In addition to these general guidelines, there have been specific efforts focused on COVID-19 vaccine trials. For example, in June 2020, the FDA offered nonbinding recommendations to the industry on development and licensure of COVID-19 vaccines that strongly encouraged the “enrollment of populations most affected by COVID-19, specifically racial and ethnic minorities.” Both Pfizer and Moderna have said they worked to ensure that people of color were included in their trials, with Moderna even slowing down enrollment to try to enroll more racial and ethnic minorities. There have also been efforts on the community side. For example, historically Black colleges and universities are participating in COVID-19 vaccine trials and encouraging participation among their communities.

How diverse are participants in COVID-19 vaccine trials?

Pfizer-BioNTech and Moderna have reported the racial/ethnic composition of the participants in the late-stage clinical trials for their COVID-19 vaccines. Pfizer-BioNTech and Moderna provided demographic data for participants in their late-stage clinical trials, including racial/ethnic composition, as part of their emergency use authorization (EUAs) applications to the FDA. These data show, that, overall, people of color are underrepresented in these trials relative to their share of the total U.S. population (Table 1), with the largest disparity among the Black population. While the trials have not included the overrepresentation of people of color that some had suggested, as noted above, these trials have achieved greater diversity than many previous trials for other drugs. In both COVID-19 trials, the demographics of the placebo and vaccine groups are similar, as are the characteristics between all participants and the safety populations (the group of individuals receiving the vaccine and followed for safety). In addition, similar vaccine efficacy results were observed across racial and ethnic groups in both the Pfizer and Moderna trials.

Total US Population Age 16+ Pfizer-BioNTech* Moderna
Total 258 million 40,277 27,817
White 73.6% 81.9% 79.4%
Black 12.3% 9.8% 9.7%
Asian 5.9% 4.4% 4.7%
American Indian/Alaska Native 0.8% 0.6% 0.8%
Native Hawaiian or Other Pacific Islander 0.2% 0.2% 0.2%
Hispanic 17.6% 26.2% 20.0%
Non-Hispanic 82.4% 73.2% 79.1%
NOTES: *Pfizer-BioNTech data are for all participants globally; of which 76.7% are in the United States. Pfizer results provided for Phase 2/3 trial, Moderna results for Phase 3 trial. The Pfizer trial included those ages 16 and older. The Moderna trial included those ages 18 and older.
SOURCES: Racial/ethnic distribution of total population age 16 or older based on KFF analysis of 2019 American Community Survey data; FDA, Briefing Document: Pfizer-BioNTech COVID-19 Vaccine, December 10, 2020; FDA, Briefing Document: Moderna COVID-19 Vaccine, December 17, 2020

What are implications of diversity in COVID-19 vaccine trials for vaccination efforts?

These data show that although people of color are underrepresented in the clinical trials for the two initial COVID-19 vaccines compared to their share of the population, the trials include people from diverse racial/ethnic backgrounds and are more diverse than some trials have historically been. The findings showing that vaccine safety and efficacy were similar for people of color and White participants could help increase confidence in willingness to get the vaccine, particularly among Black adults who are more likely than White adults to point to concerns about safety and side effects as major reasons for why they probably or definitely would not get the vaccine. As such, information on the diversity of participants in the clinical trials and the trials’ findings on safety and efficacy for people of color could be an important component of outreach and education campaigns and vaccination efforts that could help prevent disparities in vaccination.

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