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UK Clinical Trial Diversity Gap: The Impact of Cost and Payment

Randa Bennett

September 12, 2026

1. Introduction: Diversity in Clinical Trials is Impacted by Cost and Payment

Why does diversity in clinical trials matter?

Clinical trial participants determine who a medicine or vaccine is proven to work for. When the people taking part in research do not reflect the population that will eventually use the treatment, the evidence itself has a gap built into it.

That gap is measurable. Ipsos research shows that 58% of UK adults say they would be willing to join a clinical trial, but this falls to 41% among adults from ethnic minority backgrounds.

This is happening as overall participation is also shrinking. NHS commercial trial recruitment has fallen for four consecutive years, to its lowest level since 2017/18, and only around one in ten medicines that enter trials reach Phase III. Fewer people are taking part overall, and those who do are not representative of the population the NHS serves.

This paper looks at where cost and payment sit within that problem, and what the evidence says actually motivates ethnic minority participation, rather than what is commonly assumed.

2. The Invitation Gap in the UK Clinical Trials

Q: Are ethnic minority adults less likely to take part in UK clinical trials once invited?

A: Yes. Ipsos research shows that when ethnic minority adults are invited to take part in a clinical trial, 36% go on to participate, compared with 44% of White adults invited.

Willingness to participate is only part of the story. Even when ethnic minority adults are invited to take part in a trial, fewer go on to do so.

This gap does not close once someone is invited. It shows up again in the trials themselves: a meta-analysis of 30 UK-based COVID-19 trials, covering almost 119,000 participants, found Black participants made up 1% of enrolment against an expected 3.3% based on census figures, and Asian participants 5.8% against an expected 7.5%.

3. Why Representation in Clinical Trials Matters for Patient Safety

Q: Why does a lack of diversity in clinical trials cause real harm?

A: When trial data comes mainly from one population, the results do not always hold for everyone else. Two examples from UK healthcare show what that gap costs in practice: less accurate diabetes testing in some Black men, and pulse oximeters that overestimated oxygen levels in patients with darker skin during COVID-19.

Under-representation in a trial does not just mean fewer people from a group took part. It can mean the treatment or test was never properly proven to work for them in the first place.

Dr Veline L'Esperance has pointed to genetic differences in some Black men that affect the accuracy of standard diabetes testing, leading to delayed diagnosis. Dr Bola Owolabi has highlighted a similar problem during COVID-19: pulse oximeters, widely used in homes and hospitals, were less accurate for people with darker skin, often overestimating oxygen saturation. Some patients had dangerously low oxygen levels the devices did not detect, which delayed their care.

4. Cost as a Barrier to Clinical Trial Participation in the UK

Q: Is cost a barrier to clinical trial participation for ethnic minority adults?

A: Yes, but not evenly. Ipsos research found that 28% of UK adults are concerned about the cost of taking part in a clinical trial. That concern did not vary notably by income, and the clearest split in the data sat within a single ethnic group: 32% of Asian men cited cost as a concern, against 20% of Asian women.

Cost is a real barrier to participation, but it does not affect everyone in the same way. Concern about cost was similar across income levels, and the clearest difference was not between ethnic groups but within one, between men and women.

This suggests a flat, one-size approach to cost will not close the gap on its own. What matters is not just whether cost is addressed, but how it is addressed. The next section looks at what the evidence says actually motivates ethnic minority participation.

5. What Motivates Clinical Trial Participation in the UK

Q: What motivates ethnic minority adults to take part in UK clinical trials?

A: Ipsos research found that ensuring payment for travel or missed work was significantly more important in motivating clinical trial participation for ethnic minority adults, and this held across income levels. Clear communication about trial logistics, and about when and how participants will be paid, was also identified as vitally important.

Section 4 showed that cost concern does not split cleanly by ethnicity or income. This section shows something more specific: payment for travel and missed work is a stronger motivator for ethnic minority adults than for the population overall, and that holds true regardless of how much someone earns.

The same research points to a second factor alongside payment itself: clarity. Participants who understand the logistics of a trial, and know when and how they will be paid, are more likely to take part. Payment and communication about payment appear to work together, not separately.

6. UK Regulation on Clinical Trial Diversity and Inclusion

Q: Is the UK regulating for diversity in clinical trials?

A: Yes. The Health Research Authority and the Medicines and Healthcare products Regulatory Agency are developing an Inclusion and Diversity Plan, working with the National Institute for Health and Care Research. Separately, the NIHR-INCLUDE framework names geography and cost of travel as explicit barriers for under-served groups.

The findings in this paper are not new to the regulators. The HRA and MHRA are jointly developing an Inclusion and Diversity Plan for researchers and sponsors to complete, designed to be applied from the earliest stages of trial design rather than added afterwards. It is being developed with input from the NIHR, and UK officials have described its scope as wider than the equivalent US approach, asking researchers to consider factors beyond race and ethnicity alone.

The NIHR-INCLUDE framework adds detail to this. It sets out who counts as an under-served group and names specific barriers to their inclusion, among them where people live and the cost of travelling to a trial site. This gives the payment and logistics findings in section 4 a direct link to current UK policy, rather than leaving them as a standalone research finding.

7. What Good Looks Like: Closing the Clinical Trial Diversity Gap

Q: What can sponsors and sites do to address cost as a barrier to clinical trial diversity?

A: The evidence points to two practical steps: pay participants for travel and missed work reliably, and communicate clearly, early, on when and how that payment will happen.

This paper has focused on cost and payment. It is one part of a wider picture that includes trust in the health system, awareness, and how people are referred into trials in the first place, among other factors, but in relation to cost, the evidence points to two clear actions:

1. Pay for travel and missed work
Not just a general stipend. This is the specific cost shown to motivate ethnic minority participation, across income levels.

2. Tell participants when and how they will be paid
Before they need to ask. Clarity on logistics and payment was found to be as important as the payment itself.

8. Conclusion

Meet Priya.

Priya is 34. She works shifts at a warehouse in Leicester, paid by the hour. She was invited to take part in a trial for a new asthma treatment after years of managing it herself with an inhaler and guesswork. Her mother has the same condition. Priya wants better answers for her own daughter, in case she inherits it too.

The trial is run from a clinic in Nottingham. An off-peak train ticket costs £15 each way. A taxi from the station to the clinic costs £12 each way. That is £27 each way, £54 for the round trip, on top of a full day's unpaid leave from her shift work.

She asks the coordinator what she will get back for the day. The coordinator is not sure, and says someone will be in touch about the expenses process.

Nobody is in touch at the visit. Priya pays the £54 herself and travels home. Two days later, an email arrives with a form to fill in and a request for receipts. She has not kept them, because nobody told her at the visit that she would need to.

She means to sort it. But finding the receipts, or working out what to do without them, keeps slipping down her list. The form sits unopened.

She is invited back for a second visit. She thinks about the £54 it will cost her again, and the form from the first visit she still has not dealt with. Does she spend the money a second time, on the hope that this time it comes back to her? Or does she just leave it?

She leaves it.

Nobody made a decision to lose Priya. No one told her the trial did not want her. But nobody told her, clearly and at the point it mattered, that she would be paid, how much, or when. So she assumed the worst, and on the evidence available to her, she was right to.

That is the gap this paper has been describing. Priya was not put off by the size of a stipend. She was put off by not knowing, and then by a process that made her chase money she had already spent.

Payment build for Clinical Trial Participants

The evidence in this paper points to something practical: participants take part when they trust they will be paid, and told clearly when and how. That is what we focus on at vHelp. We pay participants directly to their bank account, confirm every payment clearly, and give sponsors one system for handling it.

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