TORONTO -- As Canadians mark their seventh week of living amidst a pandemic, many have placed their optimism in the unprecedented global efforts to develop a vaccine for COVID-19.

Drug companies and scientists all over the world are actively engaged in this call to arms, with at least five candidate vaccines in clinical evaluation and another 71 in clinical preclinical evaluation, according to the World Health Organization (WHO).

With governments, research bodies and philanthropists throwing billions of dollars at vaccine development, experts have estimated that a COVID-19 vaccine could be ready in 12 to 18 months.

But, experts warn that much may still stand in the way of delivering a successful vaccine candidate to billions of people worldwide.

“You've got an international collaboration that is very different than anything we've seen before, so the timeframe for finding a vaccine seems reasonable,” Alison Thompson, associate professor at the University of Toronto’s Leslie Dan Faculty of Pharmacy, told by phone.

“What slows it down and is really how much safety testing you want to do.”

When considering the economic and mental health repercussions of the coronavirus pandemic, 18 months might sound like a long time. But in the world of vaccinations, it’s akin to a blink.

The mumps vaccine, largely considered to be the fastest ever approved, took four years to become widely available, from development to licensing of a drug in 1967.

Thompson notes that rushing a vaccine has had deadly repercussions in the past.

In 1976, the U.S. government rushed to develop a swine flu vaccination over fears of the next big pandemic. The immunization program was halted after 10 weeks due to reports that the vaccination increased the risk for Guillain-Barre syndrome, a rare form of paralysis that starts in the feet and creeps up the body.

More than 450 people developed Guillain-Barre syndrome after receiving the vaccine; 25 died.

“We could rush something to market really quickly and have a repeat of the swine flu vaccine debacle, where the vaccine killed more people than the virus,” Thompson said.

“Part of the safety concern is that the risk-benefit ratio is different for a vaccine because it's usually put into healthy people. The standard is much higher than it would be for a therapeutic drug that's trying to treat something where you're already sick.”

Vaccines require preclinical testing in animals and three phases of clinical trial evaluations in humans before completion. The first stages of the earliest COVID-19 trials aren’t due for completion until the fall or later, but several have already begun clinical trials.

Some teams are clearing hurdles faster than others. Scientists at Oxford University, for example, are moving forward with a clinical trial that will involve nearly 6,000 people, testing a new variation of a vaccine that has proven safe in humans previously.

The Oxford team says that with emergency approval from regulators, large-scale manufacturing could be carried out while the clinical trial is ongoing, allowing them to develop a million doses of the vaccine by September.

But scientists note we must remain cautious when mapping out a timeline.

“The best-case scenario is that by the autumn of 2020 we could have an efficacy result from the phase III trial to show that the vaccine protects against the virus, alongside the ability to manufacture large amounts of the vaccine,” the Oxford team noted in early April, noting the ability to determine the vaccine’s efficacy will rely heavily on transmissions within the local population over the summer.

“But these best-case timeframes are highly ambitious and subject to change.”


Beyond testing, the prospect of manufacturing billions of vaccines remains a sticking point for experts.

“The volume of vaccine that needs to be made is unprecedented, if everyone has to have it, which is another question,” Natasha Crowcroft, chief of applied immunization research and evaluation at Public Health Ontario, told by phone.

Crowcroft says the federal government has made substantial investments in vaccine research, bolstering our ability to produce a vaccine locally when it becomes available. That funding includes $23 million to support pre-clinical testing and clinical trials of a potential COVID-19 vaccine in Canada and $29 million for the production of vaccines.

But if a large percentage of the global population requires inoculations, we’ll have to get creative.

Crowcroft notes there have been some suggestions of retooling industries that are in trouble now and trying to see how they can help with vaccine manufacturing. But several questions remain, including impacts on the production of other drugs and vaccines.

“We have a real issue right now with the whole childhood immunization program is grinding to a halt because of COVID-19,” she said.

“Kids who are not badly affected by COVID-19 are then at risk of getting all these other principal diseases that they are at risk of.”

She notes health officials will also have to weigh the repercussions of limiting the production of seasonal flu vaccines in favour of the COVID-19 vaccine.


The ethics of how a vaccine would be produced and distributed around the world bring up several ethical concerns.

Many experts have called for a global access agreement to be developed in order to guarantee that vulnerable populations, including the elderly, health-care workers, and people in resource-poor epicenters, have priority access to the vaccine.

This model has proved effective with past vaccines, including the Ebola vaccination that was developed in Canada, shared with researchers and biotech companies in the U.S. and later manufactured in Germany.

Thompson notes that governments will be largely responsible for deciding which segments of the population should receive the vaccine first.

On Tuesday, Prime Minister Justin Trudeau said Canada is already preparing production capacity for a vaccine, but would not speculate on who would receive a vaccine.

“We already know that countries around the world will be producing for their own citizens first, and we need to be part of that as well,” he said.

“In terms of what kinds of vaccination protocols will be in place, we still have a fair bit of time to reflect on that in order to get it right.”

Reports that the U.S. allegedly attempted to buy exclusive rights to vaccine research being carried out by a German firm have also highlighted important ethics surrounding access to a vaccine.

“We really need to have the conversation about nationalism and protecting your own citizens first -- is that the most ethical response here, when there may be certain populations in the world that are really, really suffering the most,” she said.

“What are our international obligations to global health? It is a big question here.”