For first time in Canada, researchers deliberately infect volunteers with flu to advance vaccine research
A controlled human infection study in Montreal and Halifax aims to speed vaccine development—but participants must isolate for a week.
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Canada has launched its first controlled human infection study, deliberately exposing healthy volunteers to influenza under carefully controlled conditions to accelerate vaccine research and pandemic preparedness.
The study began in Halifax in June and started its Montreal phase in the last week of September. Researchers at the Canadian Center for Vaccinology in Halifax and the Montreal site are recruiting healthy adults aged 18 to 45 with no increased risk of severe flu. Participants give informed consent and are deliberately exposed to a well-characterized seasonal influenza virus delivered through the nose. Some receive a placebo—saline—instead.
Volunteers are placed in individual negative-pressure rooms and monitored closely by health-care professionals for at least seven days. Researchers start with a lower viral dose before escalating to a higher dose. At the higher dose, between 60 and 70 per cent of virus-exposed participants are expected to develop mild-to-moderate influenza illness. Participants can receive antiviral medication if needed and must test negative for influenza on two consecutive days before leaving the isolation unit.
An independent Data and Safety Monitoring Board reviews safety data before each dose escalation. Dr. Brian Ward, co-principal investigator and Director of the MUHC Vaccine Study Centre, explained the rationale: "Conventional vaccine development ultimately relies on large field efficacy trials in which researchers wait for participants to be naturally exposed to the virus. Those trials can be lengthy and expensive. With this study, we will be able to learn in days what is difficult to observe in a field trial."
The immediate goal is to establish a reliable influenza infection model and collect safety, virological, and immune-response data. A secondary objective is to help Canada develop domestic capacity to manufacture challenge viruses for research—reducing reliance on viruses produced outside the country. "Developing this specialized expertise domestically using a seasonal influenza virus could eventually allow Canadian researchers to produce new challenge strains more rapidly—including strains relevant to an emerging seasonal or pandemic threat," said Dr. Scott Halperin, co-principal investigator at Dalhousie University.
The study underwent independent scientific and ethical review before participant enrollment began. As HOC reported in September, Quebec announced it won't administer free flu shots this fall.
How many total participants does the study plan to enroll, and what is the timeline to completion?
Has Canada approved other controlled human infection model studies before this one?
We'll update this story as answers emerge.
The facts
Who can participate in this flu study?
Healthy adults aged 18 to 45 with no increased risk of severe flu are eligible. All participants must give informed consent before being deliberately exposed to influenza.
What happens to participants during the study?
Volunteers are placed in individual negative-pressure rooms and monitored by health-care professionals for at least seven days. Researchers start with a lower viral dose and may escalate to a higher dose, where 60 to 70 per cent of exposed participants are expected to develop mild-to-moderate influenza. Participants must test negative for influenza on two consecutive days before leaving isolation.
Why is Canada doing this type of study instead of waiting for natural virus exposure?
Conventional vaccine development requires lengthy and expensive field trials where researchers wait for participants to be naturally exposed to the virus. This controlled study allows researchers to learn in days what is difficult to observe in a field trial.
