Canada lags behind on third doses
Enthusiasm has tapered off for boosters, as other countries have begun offering fourth shots
The days of the two- shot COVID vaccine regime appear all but over, with countries such as Israel and now the United States opening up widespread access to not just a third shot to bolster waning protection against infection, but a fourth.
It’s left some experts wondering whether Canada, which worked hard to get those first two shots into arms, is now falling behind in the push to vaccinate its citizens.
The U. S. Food and Drug Administration this week approved a fourth shot for people 50 and older in the U. S. While at least Pfizer says it has begun conversations with Health Canada, the regulatory body has yet to see an official application for that cohort to get a fourth dose from anyone.
Meanwhile, a sub- variant of highly infectious Omicron has upended what we knew about the virus — again — meaning that, at least for high- risk people, vaccination is looking less like a milestone to be achieved, and more like a process to be maintained.
That’s a message that may not yet have widespread acceptance in Canada, where 85 per cent of people have two doses but just under half have rolled up their sleeves for a third.
“I think people feel like they did their part,” said Dr. Tara Kiran, a family doctor at St. Michael’s Hospital and the Fidani Chair in improvement and innovation at the University of Toronto.
“They got their first and second doses, and maybe they were even on the fence, but they were like, ‘ I’m going to roll up my sleeves and do it, because it’s important.’”
But when it comes to a third, or even fourth dose, that enthusiasm has tapered off, especially after a concerted push from health- care workers when Omicron landed in December, Kiran said.
Kiran pointed to a combination of mixed messaging — the federal government still defines two doses as being “fully vaccinated” — confusion about why more vaccinated people are getting sick, and good old- fashioned fatigue.
In several key ways, Omicron — and its sub- variant BA. 2, which is now dominant in much of the world — has changed the vaccination game. The fact that more vaccinated people now seem to be getting sick doesn’t mean the vaccines aren’t working, experts say, but it does mean that those who are high risk should be considering a booster.
To understand what’s happening, it’s important to know that vaccines have had two different but critical functions. First, if you get exposed to COVID, the shot helps your body muster a rapid response, using antibodies, to fight off an attempted infection.
But if the virus does sneak past those defences? The vaccine will also have prepped your T cells, which are a slower- acting but longerlasting immune response, to help make sure your illness isn’t as serious.
It’s that first type of protection that is weakening over time, says Tara Moriarty, an infectious disease expert and associate professor at the University of Toronto.
That’s pretty typical of vaccines, she says. After all, your body doesn’t really have the space or energy to keep all the antibodies it’s ever made forever. But while the slower acting T cell response seems to be holding, Omicron is so spreadable and fast- acting that it’s proven especially good at slipping past that first line of defence, she adds.
That means that vaccinated people are now more likely to get sick — and that protection against infection is dropping by as much as two per cent per week, she says. Vaccinated people are still less likely to get seriously ill, but anytime you have more sick people, it holds that a greater share will, statistically, get really, seriously sick.
Moriarty, who helps host weekly Zoom sessions where anyone can ask a volunteer scientist questions about vaccines, says she’s not sure that message is getting through to the average person.
“In Canada right now, assuming that people are not going to get reinfected ( if they’ve already had COVID once), which is not true, there is probably about 50 per cent of people 40 and older who are still susceptible to infection because they don’t have their booster or they haven’t been infected already,” Moriarty said.
Health Canada has authorized both the Moderna and Pfizer vaccines as booster, or third shots, to be taken at least six months after the first two.
In guidance on booster shots released in December, the national advisory group said that data on a fourth shot was “limited,” but that immunocompromised people needed three shots where other people needed two, so they could also receive a fourth shot as a booster.
Other countries have far outpaced Canada on third, and now fourth shots.
In Chile, more than 80 per cent of people had a third shot, though officials mixed types of vaccines, and the country was the first in Latin America to offer fourth shots. In December, Singapore began requiring people to have a third dose to be considered fully vaccinated, and now has more than 70 per cent uptake.
The global average, according to Our World In Data, is about 20 per cent.
Meanwhile, other countries have now taken it a step further: The U. S. has authorized a fourth shot for those over 50 and the U. K. is recommending a fourth for people over 75, who live in a care home or who are immunocompromised.
While several provinces, Ontario, Quebec and Alberta among them, are offering fourth doses to certain people who are immunocompromised, there is no national guidance yet.
“From a health- care provider standpoint, you’re obviously not going to advertise to patients that this is coming until you get a recommendation,” said Dr. Zain Chagla, an infectious diseases doctor with McMaster University.
While the dominance of Omicron means the vaccines are not as good at preventing transmission, they remain good at preventing serious illness, he says. That means that when fourth doses become more widely available in Canada it will be important to make sure they go to people who need them most — those who are older or otherwise immunocompromised.
“I think people can still have trust if they’ve gotten three doses, or even two doses and have some natural immunity, I think they have really, really good protection against the severe outcomes here,” he said.
“But I think there is some need for the older population, those with medical conditions, those who are immunocompromised, to make sure that their doses are up to date.”