Marcus Dahl, an Australian living and working in the UK, decided to join his first clinical trial in about five minutes. A friend at Oxford’s school of public health had forwarded him a recruitment newsletter. “She said, this looks like… [a] thing you would do,” he recalls. She was right. He clicked the link and signed up.
The study was a COVID-19 human challenge trial run at Oxford in 2021. In a challenge study, a small number of healthy, closely monitored volunteers are deliberately exposed to a pathogen so researchers can study how the disease behaves and how to defend against it. In the case of a COVID-19 trial, that meant a seventeen-day quarantine in a hospital isolation room. But Marcus nonetheless found enrolling to be an easy decision. “The COVID pandemic was killing millions of people. It was a massive global challenge… leading researchers in Oxford were trying to figure it out,” he recalls. He was very happy to support their efforts.
Part of what made the choice straightforward was Marcus’ recognition of his own good fortune at a time when many were suffering. He lived near leading research universities, was in good health, and had a flexible schedule. As he puts it: “I was in the perfect position to sign up for this kind of thing, and to try and do my part to contribute to important medical research. I’m not qualified in medicine, so this is what I can do to support it.”
He also started to use his experience to contribute to vaccine development research in other ways. COVID research was drawing media attention, so Marcus used his seventeen days in quarantine to run a fundraiser for UNICEF’s COVAX programme and eventually donated his entire study compensation to the cause.
Marcus is not a one-time volunteer. Over several years at Oxford he put himself forward for four challenge studies and was accepted into two. Even willing, healthy volunteers, he notes, are sometimes screened out. His second completed study, in 2025, was for a new tuberculosis vaccine. This trial involved a six-month, outpatient commitment and used an inhaled, aerosolised form of BCG, administered in isolation to measure the immune response.
Across both trials, Marcus was struck by how carefully they were run. “It felt to me like what I would imagine best practice to look like. I felt very well informed and looked after at all times.” He remembers being quizzed on the participant information sheet to confirm he had actually read it—ensuring that his consent was completely informed—and his gratitude towards a team that pushed his screening back a couple of weeks when it collided with his Master’s exams. “All the nurses and doctors were very kind, and the food was great,” he notes.
It felt to me like what I would imagine best practice to look like. I felt very well informed and looked after at all times.
Research Participation: Two challenge studies at Oxford – COVID-19 live virus human challenge trial (2021) and novel tuberculosis vaccine trial (2025)
Passionate About: Ethics, advocacy, and encouraging more participation in medical research through better communication and outreach
Outside the Council: Nature photography
His Friends Describe Him as: Thoughtful, diligent, and smiley
That first-hand knowledge shapes how he responds to people who express concern about the safety of his trial participation. “Unless they’ve read a participant information sheet,” he explained, “they might not fully understand how much thought and care has gone into planning these trials.” The possibility of helping prospective participants understand the care that goes into participant-centered trial design drew Marcus towards advocacy.
Marcus grew up in Sydney and moved to the UK in 2020 to pursue a Master’s at Oxford. He has since completed a PhD in human rights law and now works in London as a public inquiries lawyer. Ethics, he says, is something he cares about “as a lawyer and as an individual.”
That mix of legal training and lived experience informs his role as a member of 1Day Sooner’s Participant Council, an international body of healthy volunteers brought together to ensure participants have a meaningful voice in the research that depends on them. Marcus first heard about 1Day Sooner from a doctor at the end of his COVID quarantine. “One of the doctors said this organization is interested in supporting and hearing the experiences of participants,” he recalls. He then looked into the organization further and stayed connected before later applying to join the Council.
As for success on the Council, Marcus’ measure is simple: “Are we talking about meaningful things? Are we doing meaningful things? Do I feel respected? Do I feel this is a useful organisation? And the answer to all of those things is yes.” Marcus feels strongly that encouraging people to enroll in clinical trials and supporting them when they do is an important part of the path to improving public health.
If you’ve participated in a clinical trial as a healthy volunteer, or are interested in doing so, 1Day Sooner wants to hear from you. You can sign up here or reach out at volunteer@1daysooner.org.