What is it about?

Human challenge trials are experiments in which people volunteer to be deliberately infected with a virus or bacteria to help test vaccines or medical treatments. Such trials can dramatically shorten the time required to test vaccines, thus potentially saving many lives. But some worry that it is unethical to ask people to volunteer for human challenge trials. Taking part in these trials can be risky, and there is a known history of trials recruiting vulnerable volunteers who need money and feel they have no choice but to volunteer, sometimes for multiple trials. Ideally, people would volunteer to take part in these trials because it is consistent with their true preferences and values. Given the altruistic nature of human challenge trials—with volunteers taking on risks in order to benefit other people—it would be better from an ethical perspective if those who volunteer have highly altruistic goals, values, and preferences. The non-profit organization 1Day Sooner was created early in the pandemic (April of 2020) to speed up vaccine development by creating a database of people willing to volunteer for human challenge trials. We surveyed a sample of these volunteers to learn why they signed up. Results suggested that they signed up for altruistic reasons. Nearly all volunteers reported altruistic motivations for volunteering. They had also engaged in other altruistic behaviors at high rates, including donating blood, donating money to charity, and registering as living marrow donors and deceased organ donors. Volunteers also scored higher in personality traits related to altruism. We found no evidence volunteers were unusually susceptible to being exploited. Together, this research suggests that the people who came forward wanting to take part in vaccine challenge trials for COVID-19 at that early point in the pandemic show reliably altruistic motivations, preferences, and values, consistent with the nature of these trials. We don’t claim this generalizes to any healthy volunteers coming forward for any trial, but our findings suggest that in an early pandemic context, where challenge trials have especially high social value and the possibility of these trials becomes highly publicized, it may be much more likely that the volunteers coming forward are motivated by altruism rather than vulnerability.

Featured Image

Why is it important?

Our findings are inconsistent with concerns expressed early in the COVID-19 pandemic that human challenge trials with the novel coronavirus would be unethical. Recruitment for such trials could be viewed as inherently exploitative if it attracted volunteers who were financially desperate, had difficulty judging the risks, or who were otherwise vulnerable to exploitation. Our results indicate that such trials, in principle, could attract volunteers who are instead primarily motivated by altruism and do not exhibit any indicators of socioeconomic or psychological vulnerability to exploitation. In finding that COVID-19 human challenge trials can attract volunteers whose altruistic preferences and values are aligned with the nature of these trials (and who are not unusually vulnerable to exploitation), this research may allay ethical concerns about the volunteers interested in participating in COVID-19 human challenge trials. Moreover, similarly altruistically motivated volunteers may come forward in the early stages of future pandemics, when the social value of human challenge trials is arguably highest. Our findings may therefore reduce barriers to setting up future vaccine challenge trials, which may speed the development of effective vaccines.


I have conducted research for many years on the psychology and neuroscience of altruism, particularly why people make altruistic decisions in the biomedical realm--for example, to donate their blood, bone marrow, or an organ to a stranger. When the COVID-19 pandemic struck, I, like many others, was eager to help reduce the suffering it was causing in any way that I could. It was a pleasure to join forces with my co-authors of this study, including the founder of 1 Day Sooner and many members of the organization's board to conduct research on the motivations and personalities of challenge trial volunteers, the results of which support the ethics of conducting these trials and may promote their use in developing future vaccines and other medical treatments.

Abigail Marsh
Georgetown University

Read the Original

This page is a summary of: Characterizing altruistic motivation in potential volunteers for SARS-CoV-2 challenge trials, PLoS ONE, November 2022, PLOS,
DOI: 10.1371/journal.pone.0275823.
You can read the full text:

Open access logo



The following have contributed to this page