Human trials may offer a pathway toward a COVID-19 vaccine, but the effort is rife with ethical pitfalls that need to be navigated. It is a journey that requires a well-developed roadmap forward, according to one Western researcher.
Western scholar Charles Weijer joined an international team that developed Key criteria for the ethical acceptability of COVID-19 human challenge studies, a 19-page set of guidelines issued by the World Health Organization (WHO) earlier this month.
“Even with all of the important public-health interventions that have been implemented, there is a strong sense that we, as a society, are not going to get past the COVID-19 threat until there is a widely available and effective vaccine for the virus,” said Weijer, a professor in the departments of Medicine, Epidemiology & Biostatistics and Philosophy.
Traditional vaccine development, however, is a stepwise process that can take years to complete.
“This led a lot of people to start considering how we could speed up vaccine development and consider whether human challenge studies might be an important part of that,” Weijer said.
Human challenge studies involve intentionally infecting healthy volunteers with a disease to test potential treatments or vaccines. They allow us to test vaccine candidates quickly and identify the most promising among them for field trials. Human challenge studies have been carried out for decades in highly controlled laboratory environments for diseases like malaria, influenza and cholera.
In 2015, Weijer and colleagues published an ethical framework for human challenge studies that included a clear limit on risk to participants: they may not be exposed to a potentially fatal disease unless there is a curative treatment.
But the current pandemic is different.
“Unfortunately, there is no curative treatment for COVID-19 at the moment and it is a disease associated with a risk of serious illness and death,” Weijer said. “At first, this was a real impediment for us, leading us to ask, ‘Is there any way in which the risk of these studies could be justified for COVID-19?’”
As part of the WHO Working Group for Guidance on Human Challenge Studies, Weijer along with 13 other international experts began working on this question in late March.
The document produced by the WHO Working Group outlines eight criteria that must be met for a COVID-19 human challenge study to be ethically justified, including restricting participation to healthy people aged 18-29 and setting high standards for informed consent. The guidelines notably do not rule out challenge trials in the absence of an effective treatment, instead stating the risk should fall within acceptable limits.
With COVID-19 circulating in a community, there is a significant risk for an individual to be infected with the virus outside of the study. If a research participant has a high probability of contracting the virus regardless of their trial participation, it may make purposefully infecting them ethically permissible.
“This helps explain why it is potentially permissible to do riskier studies in the face of a pandemic. If people have a good chance of being infected outside of the human challenge study, it offsets the risk of them being exposed for research purposes,” he said.