Dressed in a fully enclosed pressure suit, like an astronaut in space, a virologist at the Université de Montréal Hospital Research Centre peers into a microscope.
Here on the fourth floor of the research centre, he anxiously watches to see if the antibodies generated by a COVID-19 vaccine can fend off a live sample of the novel coronavirus, which has killed more than 27,500 Canadians.
The research, which is being overseen by professors Andrés Finzi and Daniel Kaufmann from the Université de Montréal, could help answer key questions scientists around the world are grappling with: who needs a third shot of the COVID-19 vaccine? And when might they need it?
WATCH: Antibodies only half the story of vaccine protection: experts
Finzi and Kaufmann’s teams are following a small group of healthcare workers, just over 40, half of whom were previously infected with COVID-19, the other having never encountered the virus — all of whom received two doses of the Pfizer-BioNTech vaccine.
Their findings show the vaccine produces a robust immune response and is holding up against infections.
“Up to six months, past vaccination, studies from the U.S. and other places — and we are getting similar results — we are measuring that the cellular responses are there,” Finzi told Global News’ current affairs show The New Reality.
Read more: An exclusive look inside Moderna
International researchers, like those from the Université de Montréal, have been studying the blood of individuals to help understand the immune response to COVID-19 vaccines and how long they may provide protection.
“We are trying to understand how these antibodies are being elicited, how rapidly they come up and how long do they stay?” Finzi explained.
“And is it possible that the interval between the doses may affect how good (the response) is?”
In the face of surging caseloads, driven by the highly infectious Delta variant, some health agencies have moved quickly to offer third doses to the elderly or immunocompromised, even as most countries have seen pandemics “among the unvaccinated.”
However, the debate among public health experts over whether a booster dose is needed for healthy adults — and when they should be given — is divisive.
The Israeli test case
Israel became one of the first, real-world test cases for COVID-19 vaccinations by locking in a supply of the Pfizer-BioNTech vaccine with a unique deal: vaccines for data, according to a publicly released contract.
Now the country has found itself at the centre of a raging global debate around the need for boosters.
Over the summer, the country saw a surge in cases, fuelled by the Delta variant, which included thousands who were fully vaccinated.
Israeli lawmakers responded by authorizing third doses for those 60 and over in late July before extending that to everyone 12 and older by the end of August. They are now even considering fourth doses, according to statements from Israeli health officials.
Jonathan Halevy, president of Jerusalem’s Shaare Zedek Medical Center, said that since the booster campaign began, the country has seen a decline in hospitalizations.
“We’ve seen the effect of the booster and the excellent protection it gives against severe disease,” Halevy said.
Other countries, like the U.K., France, Germany, and Denmark, have taken more targeted approaches by offering third doses to vulnerable citizens like the immunocompromised and the elderly.
In the U.S., President Joe Biden’s administration had planned to offer another round of shots to all fully vaccinated Americans, but the Centers for Disease Control ultimately rejected boosters for the general public, authorizing additional Pfizer-BioNTech doses only for people over 65, as well as those who are deemed high-risk, such as health care workers and teachers.
Canada’s National Advisory Committee on Immunization (NACI) has only approved additional shots for immunocompromised people and people living in long-term care homes.
At the B.C Centre for Disease Control, Dr. Danuta Skowronski, the epidemiological lead, is among a group of scientists who are skeptical about the need for boosters.
“Like a detective, we have to be very careful not to be fooled by what we may sense at first glance,” she said.
Skowronski has been tracking vaccine effectiveness in B.C. in real-time using a method her team first created for influenza in 2004 and is now used in 25 countries.
Her data showed both the Moderna and Pfizer-BioNTech vaccines are offering “terrific” protection against the virus.
Dr. Skowronski’s team collected data from nearly 247,000 people in B.C. from May 30 – Sept. 11, coinciding with the rise of the Delta variant.
Two doses of both the Pfizer-BioNTech and Moderna vaccines were 98 per cent effective at preventing hospitalizations, while AstraZeneca was 93 per cent effective, according to the data.
“It’s important to remember that the goal of the COVID-19 vaccination program is not to eliminate the virus,” she said. “The goal of the program is to minimize hospitalizations, deaths, and severe outcomes.”
“We’re not concerned if people have the sniffles,” she said.
The data also indicated the effectiveness of the Pfizer-BioNTech vaccine jumped from 82 per cent to 92 per cent when the spacing between doses was more than six weeks.
The Canadian experience is a unique one. Many provinces elected to space out first and second doses by up to four months. Skowronski said this move had an impact on the durability of the vaccine — and in turn, our need for a booster.
“It does appear to have optimized the second dose protection in the fall, now when we most need it,” she said.
Extending the dose interval
Back in Montreal, Kaufmann and Finzi’s teams also found that extending the dose interval to 16 weeks elicited a strong immune response.
“The dosing interval is actually a critical component of the immune response being generated by these vaccines,” Finzi said.
While some studies point to waning antibodies over time, Kaufmann said that B-cells and T-cells continue to work together to stave off severe disease after the vaccine is administered.
These cells can remain “dormant” for periods of time, but will spring into action if they see a harmful pathogen.
“The memory cells wake up and then begin to produce antibodies again,” Kaufmann said. “They can do that very rapidly and very efficiently.”
As countries assess the need for boosters, policymakers are also weighing safety concerns.
A review published last month in the Lancet, by a group of international scientists, which included departing F.D.A. officials, sharply criticized the push for boosters on several fronts.
It highlighted the health risks if boosters are introduced widely too soon, or too frequently, including rare side-effects like myocarditis — an inflammation of the heart muscle — which has been documented following first and second mRNA doses.
“If unnecessary boosting causes significant adverse reactions, there could be implications for vaccine acceptance that go beyond COVID-19 vaccines,” the authors said. “Widespread boosting should be undertaken only if there is clear evidence that it is appropriate.”
The scientists analyzed dozens of studies and said none of the preliminary data or studies provide “credible evidence of substantially declining protection against severe disease.”
Both Moderna and Pfizer-BioNTech say they saw no serious side effects, like myocarditis, in their clinical trials of boosters.
However, Ontario took steps this week to recommend Pfizer-BioNTech shots over Moderna for those aged 18 to 24 “out of an abundance of caution”.
The province said between June and August the risk of myocarditis and pericarditis for men aged 18 to 24 following a second dose of Moderna was one in 5,000. There have been no fatalities.
The risk for people who received the Pfizer-BioNTech vaccine was one in 28,000, according to the province.
Dr. Kieran Moore, Ontario’s chief medical officer of health, said Moderna’s elevated risk is “very mild” and he had “complete confidence” in the vaccine.
An ‘ethical nightmare’
Meanwhile, as the vaccination rates among wealthy countries soar, some have questioned the ethics of third doses, as developing nations struggle to get first shots.
University of Toronto bioethicist Kerry Bowman described it as an “ethical nightmare” as doctors, health care workers, and vulnerable residents in poorer countries wait for supply.
“We’re all scrambling to protect our own and we’re missing the larger picture that this is a global pandemic and global strategies will get us out of this pandemic,” Bowman said.
“It’s a pandemic of greed.”
Covax, the United Nations-backed program to vaccinate the world against COVID-19, dramatically cut its forecast for doses available in 2021 by roughly a quarter last month, which in part, is occurring as wealthy countries hoard vaccines.
Bowman said there are serious epidemiological concerns with leaving parts of the world unvaccinated where new, potentially more dangerous versions of the virus can emerge.
“I think it’s very myopic. Countries are looking simply at their own well-being and missing the big picture,” he said.