Racial and ethnic minority groups and adults aged 65 years and older were found to be underrepresented in vaccine clinical trials, but women were overrepresented, according to the results of a cross-sectional study published in JAMA Network Open.

Investigators used data from completed interventional vaccine trials registered and reported on ClinicalTrials.gov between 2011 and 2020. A total of 230 US-based clinical trials with 219,555 participants were examined.

Most trials were randomized and included multiple US regions (180/230), but some trials included international testing locations (48/230). Demographic data, including race/ethnicity, age, and sex, were collected, and US population data from the 2011 and 2018 American Community Surveys were used to compare the collected data.

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In 91 adult trials reporting race, White participants were overrepresented (77.9%; 95% CI, 77.4-78.4), while Black/African American participants and American Indian/Alaska Native participants were underrepresented (10.6%; 95% CI, 10.2-11.0, and 0.4%; 95% CI, 0.3-0.5, respectively).

White participants were represented in 133 of 134 trials reporting race, while 81/134 trials did not include Hawaiian or Pacific Islander participants and 65/134 trials did not include American Indian or Alaska Native participants. In adult trials reporting ethnicity, Hispanic or Latino participants were underrepresented (11.6%; 95% CI, 11.1-12.0).

In pediatric trials, Hispanic or Latino participants (22.5%; 95% CI, 21.6-23.4), Black or African American participants (10.1%; 95% CI, 9.7-10.6), and participants reporting multiple races (1.6%; 95% CI, 1.5-1.8) were underrepresented.

Among the 178 trials that recruited adults, 80 trials had an inclusion criterion of age 65 years and older, and 71 trials enrolled participants 65 years of age and older. In 170 trials that reported age as a percentage, 12.1% of participants were aged 65 years and older (95% CI, 12.0-12.3) compared with this age group representing 16.0% of the 2018 US population.

In contrast, women were overrepresented, accounting for 56.0% of participants (95% CI, 55.7-56.2) compared with this age group representing 50.8% to 51.5% of the US population.

This study revealed the importance of not only improving racial/ethnic minority group enrollment but also the need for trial investors to ensure fair and equitable enrollment. The study authors suggested that the improvement of racial/ethnic diversity in trials may be associated with vaccination rates in those groups, potentially improving education and addressing vaccine hesitancy.

Data indicated a demand for increased enrollment of older adults, especially for vaccines targeting infections known to be associated with increased morbidity and mortality in this age group.

Despite US Food and Drug Administration (FDA) recommendations and National Institutes of Health (NIH) policies, many trials were not compliant with reporting demographic characteristics of the study population. The reported gaps in participant representation demonstrated inclusion and diversity challenges among clinical vaccine trials due to study enrollment conducted prior to the implementation of the updated regulations.

“Future studies are needed to assess whether access to and enrollment in clinical trials will lead to improved vaccination rates in these populations because not all policy changes help improve rates,” the study authors concluded.

Disclosure: One study author declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Flores LE, Frontera WR, Andrasik MP, et al. Assessment of the inclusion of racial/ethnic minority, female, and older individuals in vaccine clinical trials. JAMA Netw Open. 4(2):e2037640. doi:10.1001/jamanetworkopen.2020.37640