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What do we know about the vaccine clinical trials for people of various ethnicities and in various countries around the world?



January 19, 2021

During clinical trials for drug or vaccine development, testing is done on recruited participants in settings controlled by investigators, meaning that the studies do not necessarily reflect real-world populations and conditions. There are many factors to consider when evaluating the safety and efficacy of COVID-19 vaccines, such as race and ethnicity, sex and gender, age, and different health conditions.

Race and ethnicity are believed to be important to consider when evaluating vaccine candidates. For example, with previous vaccines for influenza, a study found that race-related differences in immune responses to the vaccines were linked to genes being expressed differently in African Americans and Caucasians. It is possible that there could be differences in immune responses to the COVID-19 vaccines, so there is a need for diverse participants in clinical trials.

Unfortunately, clinical trials have mostly recruited a limited pool of people for participation, historically as well currently. There have been efforts to diversify the race and ethnicity of participants in COVID-19 vaccine trials, but there remain inequities in who has sufficient information to provide consent as well as who has the time and resources (such as transportation access) to participate. Additionally, there can be a lack of trust for participation due to the history of exploiting racial and ethnic minorities, such as the infamous Tuskagee syphilis that hurt many African Americans in the U.S.

Globally, drug development and clinical trials have taken place mostly in countries with more financial resources, historically as well as currently. There have been efforts to address some of these inequities, such as COVID-19 vaccine manufacturers running clinical trials with participants recruited from multiple countries. Unfortunately, there is still limited data about the safety and efficacy for people in certain parts of the world, because fewer participants there have been able to participate in clinical trials.

Clinical trial participation must be diversified, in order to understand how different people around the world will be impacted when given the COVID-19 vaccines.

Context and background

There have been many calls to diversify the participation in clinical trials for COVID-19 vaccine candidates. Earlier clinical trial results for COVID-19 vaccine candidates were primarily with adult participants ages 18-55, so more data is being gathered now on children as well as older adults. Additionally, COVID-19 vaccines being given in the general population have encountered minor allergic reactions in rare cases, further highlighting the need to ensure trials include more people with various underlying health conditions so that informed decisions can be made about who can receive the vaccines safely.

Clinical trials have historically excluded diverse populations. For example, in the U.S., the National Institutes of Health (NIH) have emphasized the need to diversify the pool of clinical trial participants, addressing the lack of inclusion of women, transgender people, and communities of color. In particular, Black, Indigenous and Latinx populations are consistently underrepresented in clinical trials. One study found that out of 230 oncology clinical trials analyzed over a ten-year period, more than 76% of participants identified as White, while only 18.3% identified as Black, 6.1% identified as Hispanic, and 3.1% identified as Asian. An older study published in Nature found that 92% of the participants in clinical trials registered with the U.S. Food and Drug Administration (FDA) identified as White in 1997, and progress has been slow with the proportion of White-identifiying participants still being ~86% in 2014.

The lack of diversity in clinical trials is an issue around the world, not just in the U.S. For example, the limited participation of Asian people in U.S. based clinical trials can limit the knowledge of safety and efficacy for Asian people elsewhere in the world, with a disproportionate impact on countries with majority Asian populations. Furthermore, the lack of resources for clinical trials in low- and middle-income countries limits the understanding of vaccine safety and efficacy in settings outside of high-income countries.

Used with Permission via Health Desk, a public health hub that explains emerging COVID-19 science.

This article was written and edited by the Tayo editorial desk and has been reviewed by an independent panel of subject matter experts.

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