Most of the vaccines approved to date use either messenger RNA or DNA to coax the body’s cells to produce the spike protein, or are synthetic versions of the spike themselves. (Exceptions are those developed in China, which are inactivated virus vaccines.)
By contrast, the vaccine from Medicago, a Canada-based company majority owned by Mitsubishi Tanabe Pharma, is what’s known as a “virus-like particle.” Nearly two dozen of this type have been designed, according to data compiled by the Milken Institute, but only five have reached clinical testing and only two are in later-stage trials.
Medicago’s vaccine, which is grown in a plant that is a close relative to tobacco, uses an immune-boosting GlaxoSmithKline chemical called an adjuvant to magnify the body’s antibody response.
The companies’ trial ran in two phases, the first of which was to determine whether the vaccination regimen of two shots, spaced 21 days apart, was safe and spurred an immune response in adults with and without underlying conditions. The second enrolled and randomly assigned 24,000 volunteers to receive either that regimen or a placebo.
Beyond the headline efficacy of 71% overall, the trial also found that people who were “seronegative” for SARS-CoV-2 — indicating they had never been exposed to the virus — were 76% less likely to fall ill if they received the shot than if they received the placebo. Against the delta variant of the virus, which remains the predominant strain around the world, the shot was 75% effective, the companies said. The new omicron variant was not circulating while the trial was being conducted.
Only a “small number” of severe cases were reported from trial volunteers, and none in those who received the vaccine.
Results have not been peer-reviewed, nor published in a medical journal. Only limited information, particularly on the vaccine’s side effects, were disclosed in the companies’ press release.
Should it get approved in Canada, Medicago’s vaccine would be the fifth available for residents of that country after shots from Moderna, Pfizer, Johnson & Johnson and AstraZeneca. Despite a supply agreement with the government, the vaccine may not be used widely because of Medicago’s need to scale up manufacturing. Its plant, which should be completed in 2024, will be able to supply 1 billion doses a year.
Canada is one of the more vaccinated countries in the world, with 76% of the population fully vaccinated and 85% of those age 12 and older. But with the continued emergence of mutation-driven variants, SARS-CoV-2 is anticipated to become an endemic virus and demand for vaccines may not wane for years.
Medicago has also begun the filing process with the Food and Drug Administration, the U.K. drugs regulator and is in preliminary discussion with the World Health Organization.