Examining COVID’s impact on clinical research participant diversity

Clinical Research

The clinical research industry has long struggled with participant diversity. One study found that only 5% of Black or Asian United Kingdom residents had ever participated in a clinical trial. A study of FDA-approved vaccine trials from 2011-2020 showed that 78% of participants were white, even though only 60% of the U.S. population was. 

And then came COVID-19. Twenty-three percent fewer clinical trials were launched from March through May 2020 because of the pandemic, and many clinical researchers switched to focusing on COVID-19 vaccines and treatments.

COVID-19 forced research organisations to adapt. With many patients unable to travel, clinical trial sites initiated more remote, flexible, and hybrid trials than ever before. This shift led to increases in participant diversity, especially in vaccine trials. But research organisations need to continue building trust and improving access if they want to develop treatments that are applicable to all of the people who need them.

Clinical trial diversity improved during COVID-19 (but not enough) 

COVID-19 had a devastating impact on people from diverse backgrounds. Patients who identify as a racial or ethnic minority make up 14% of the overall UK population but made up 33% of critically ill COVID-19 patients in UK hospitals during spring 2020. In the U.S., racial and ethnic minorities make up roughly 40% of the population but made up 84% of COVID hospitalisations.

Despite these troubling statistics, clinical trials did a poor job of making sure racial minorities were represented in the initial vaccine trials. In October 2020, only 7% of people in COVID-19 vaccine trials in the UK identified as ethnic minorities.

But both Pfizer and Moderna made conscious efforts to increase the diversity of their vaccine trials. Moderna slowed down recruitment in the U.S. in September 2020 because they realised they weren’t recruiting enough Black, Asian, and Hispanic participants. Pfizer also established sites around the world (in Argentina, Brazil, Germany, Turkey, South Africa, and the U.S.) to increase their trials’ diversity.

Diversity in COVID-19 vaccine trials

This trend has global applicability. Take the U.S. for example; the chart below shows how the diversity of the average clinical trial in the U.S. compares to the diversity of the U.S. as a whole. It also shows how Pfizer and Moderna’s efforts in their vaccine trials in the U.S. resulted in improvements in participant diversity.

Race or Ethnicity US Population FDA Data for Average Trial in US Moderna’s Phase III US Trial Pfizer US Trials
White 60% 75% 66% 71%
Hispanic 18.5% 11% 20% 13%
Black 13.5% 8% 10% 10%
Asian 6% 6% 4% 6%


These statistics demonstrate that the white population continues to be overrepresented in clinical trials, but they also show that the COVID-19 vaccine trials had greater representation of Black and Latinx people than most trials. With the exception of Moderna’s weakness in recruiting Asian participants, the vaccine trials moved in the direction of greater racial diversity.

Pfizer also released participant demographics from their global trials in Argentina, Brazil, Germany, Turkey, South Africa, and the U.S. Overall, 26% of global participants were Latinx, 10% were Black, 5% were Asian, and 1% were Native American. These numbers show that people of African and Asian descent were underrepresented around the world, while people of white European descent were overrepresented.

However, these statistics also show improvements. Only 58% of participants in the Pfizer COVID-19 global vaccine trials were white. Throughout the 2010s, around 66% of participants in vaccine trials were white. Clinical trial diversity is not where it should be, but it headed in the right direction during the COVID-19 trials.

Why did clinical trial diversity improve, and how can we keep improving it? 

Research organisations made trials more accessible during the pandemic by providing remote or local study visits. Though most sites and sponsors adopted decentralised or hybrid trials out of necessity, they can also lead to greater diversity.

According to an article published in Clinical Researcher and shared by the ACRP, decentralised clinical trials increase trial participation for people from rural areas, women, and Black and Latinx people. The ability to do check-ins and patient diaries online can remove barriers to participation for people who work strict hours, care for family members, or live hours away from the closest academic medical centre.

People who live far away from major research sites or can’t take off work can also benefit from study visits at local doctors’ offices or community clinics. Cynthia Verst spoke to MedCity about how IQVIA no longer relies solely on academic medical sites to hold trials. Instead, COVID clinical trials inspired them to spread their studies to physicians’ offices in local communities.

Reaching out to underserved communities 

Working with local healthcare providers doesn’t just make trials more accessible – it can also build trust between investigators and participants. Fifty percent of Black respondents in a Research America Survey believed people don’t participate in clinical trials because of a lack of trust. Given historical abuses like the Tuskegee study and the exploitation of Henrietta Lacks, it makes sense that many diverse patients distrust clinical trials.

The clinical trial industry needs to earn the trust that they’ve lost through historical abuses. Working with physicians, especially local physicians with diverse backgrounds, can help build that trust.

Eighty-one percent of Latinx survey respondents and 74% of African American respondents said they were somewhat or very likely to participate in a clinical trial if their doctor recommended it to them. In another study, 40% of respondents said they would like to speak with a healthcare provider who shares their racial or ethnic background.

Increasing diversity during and after the COVID-19 pandemic

By using technology and increasing the participation of local physicians in clinical trials, research organisations made the COVID-19 vaccine studies more accessible and trustworthy. These strategies helped research teams cope with the pandemic. But if we continue to embrace these tactics once the pandemic ends, we’ll increase diversity by meeting patients where they are.

About the author

Cynthia Wetmore, MD, PhD, is a double board-certified physician-scientist in pediatrics and hematology/oncology/bone marrow transplantation with more than 20 years of experience in academia and industry across multiple roles and therapeutic areas in oncology and neuroscience. She currently serves as a Scientific Officer for Florence Healthcare and the Executive Medical Director of Neoleukin Therapeutics. Prior to that role, she was the Medical Director of Clinical Development at Exelixis, Inc.