Canadian scientists are now deliberately exposing healthy volunteers to influenza viruses in controlled human infection studies, a method aimed at accelerating vaccine development and preparedness for future pandemics. This approach, while promising for scientific advancement, also brings to the forefront complex ethical considerations.
The experiments involve administering a specific dose of a seasonal influenza virus to consenting adult participants. Researchers meticulously monitor their symptoms and immune responses, providing antiviral treatments if necessary. Volunteers are then housed in specialized isolation units for a minimum of one week, or until they no longer test positive for the virus. The primary goal is to gain a deeper understanding of how pathogens behave within the human body, which can lead to the refinement of existing vaccines and treatments or the creation of entirely new ones.
A Historical Approach to Medical Research
Controlled human infection studies are not a new concept; they have been employed globally for decades to test potential vaccines and treatments for various diseases, including influenza and malaria. In 2020, during the rapid spread of COVID-19, similar “human challenge trials” were conducted by scientists in the United Kingdom. These trials involved administering experimental COVID-19 vaccines to young, healthy adults and subsequently infecting them with the SARS-CoV-2 virus. At the time, with limited proven treatments available, these studies raised ethical questions regarding the potential for exploitation and coercion of participants, who were compensated financially for their involvement and subsequent quarantine.
In Canada, the idea of conducting COVID-19 challenge trials was previously put forth. Liberal Member of Parliament Marcus Powlowski, who has a background as an emergency room physician, presented a petition to Parliament signed by several Canadian infectious disease experts. The petition urged the government to outline a plan for such trials. However, the government expressed reservations, citing the significant risks associated with a novel virus that had limited treatment options and unknown long-term effects.
Navigating the Risks and Ethical Landscape
Dr. Brian Ward, a co-principal investigator for the current influenza study and director of the MUHC Vaccine Study Centre, explained the rationale behind the caution regarding COVID-19 challenge trials. “Because SARS-CoV-2 was really new — we were discovering its biology and side effects in real time — I think there was a very reasonable hesitation on the part of many virologists, myself included, to the idea we should start using it as a challenge strain,” he stated.
Traditional vaccine studies typically involve administering a vaccine or placebo to volunteers, who are then released into the general population to observe natural exposure to circulating viruses. Dr. Ward noted that this conventional method is both time-consuming and expensive. In contrast, controlled human infection studies require fewer participants and significantly less time, as they bypass the need for natural exposure.
However, Canada has historically had limited experience with these types of studies. Dr. Ward, along with his co-investigator Scott Halperin from Dalhousie University, dedicated two decades to establishing the necessary infrastructure and protocols for such research in Canada. This included securing specialized isolation facilities, obtaining appropriate challenge viruses, and cultivating the necessary scientific expertise. “And then you have to convince everyone around you this is OK to do,” Dr. Ward remarked, highlighting the multifaceted challenges involved.
The Influenza Challenge Study in Detail
The current influenza research project, a collaboration with the Canadian Centre for Vaccinology at Dalhousie University, commenced in June. The initial phase involved eight volunteers in Halifax, with two more participants joining the study in Montreal. The research is planned to eventually include 32 healthy adults, aged 18 to 45, at each of the two sites. These individuals must not have any known risk factors for severe influenza, a disease responsible for an estimated 3,500 deaths annually in Canada.
Researchers are utilizing an attenuated, or weakened, strain of the H3N2 influenza A virus. This virus is diluted in a glucose and saline solution and administered as an aerosol spray into the volunteers’ noses. “Volunteers are being intensively studied from the moment that we infect them,” Dr. Ward emphasized.
The H3N2 subtype is a significant concern, as influenza A viruses are among those capable of causing global pandemics. In this study, participants receive either a low or a high dose of the virus, with a control group receiving a saline placebo. It is anticipated that between 60% and 70% of participants receiving the higher dose will develop mild to moderate flu symptoms.
All participants are required to remain in isolation for at least seven days. They reside in specially designed negative-pressure rooms, engineered to contain any potentially infectious air or particles within the room. Continuous monitoring by nursing staff, along with regular blood tests and nasal swabs, is conducted 24/7. Dr. Ward is on standby around the clock to respond to any adverse events, stating, “If these people show any signs of getting into trouble, we will be on top of it immediately and start antivirals.”
Future Implications and Volunteer Considerations
This research aims to enhance the understanding of the human body’s immediate and ongoing responses to influenza, a virus family known for its constant mutation, making it a challenging target for vaccines compared to diseases like measles. While this specific study is not testing a vaccine, it is designed to establish a robust model for future vaccine challenge trials.
Dr. Ward highlighted the critical aspects of conducting such research: “How do you recruit people to do this kind of study? How do you convince your research ethics board this is an OK thing to do?” He envisions that in the event of a severe influenza pandemic, challenge trials could rapidly test numerous candidate vaccines to identify those offering the most effective individual protection and community transmission reduction.
Open and honest communication with volunteers is paramount. “You have to have a very frank conversation with the volunteers,” Dr. Ward advised. He acknowledged the rare but serious possibility that even healthy individuals can experience severe reactions to influenza, potentially requiring intensive care. “Because every now and then — extremely rarely, but every now and then — a healthy individual gets flu and ends up in the intensive care unit, because their body happens to react over-strenuously to that particular viral challenge.”
Dr. Ward also provided context on the inherent risks, noting that approximately 10% of the global adult population contracts influenza annually. “It’s not like we’re doing something that is unlikely to ever happen to you otherwise,” he said, while assuring that “we do everything we can do to mitigate” the risks involved.
Despite his enthusiasm for the scientific progress, Dr. Ward admitted to feeling a degree of nervousness. “It is a little bit on the edge to be working with these volunteers and trying to do good science and make sure we aren’t doing any harm,” he confessed.
Volunteers are compensated for their time and commitment, which typically spans seven to ten days. Dr. Ward did not disclose the specific remuneration amounts but stated it is commensurate with the commitment required.
