White Coat, Black Art·The Dose

Third COVID-19 shots: Who needs them and why?

Toronto infectious disease specialist Dr. Isaac Bogoch says Canada’s approach to third doses is a "reasonable first step."

Toronto infectious disease specialist says Canada’s approach to third doses is a 'reasonable first step'

Canada's National Advisory Committee on Immunization recommended booster shots for certain immunocompromised individuals last week, but hasn't reached a decision on whether to provide additional shots to the broader population. (Lars Hagberg/The Canadian Press)
Canada's vaccine advisory body has recommended booster shots for certain immunocompromised individuals. But other countries such as Israel and the U.K are offering third doses to broader segments of their populations, despite concerns about ongoing inequities in global vaccine distribution. Infectious disease specialist Dr. Isaac Bogoch takes a close look at the issues. 21:44

This week, the U.K. joined Israel and the U.S. in offering third doses to broad segments of their populations, an approach that has raised concerns about ongoing inequities in global vaccine distribution. 

Here in Canada, the National Advisory Committee on Immunization (NACI) recommended booster shots for certain immunocompromised individuals last week, but hasn't reached a decision on whether to provide additional shots to the broader population.

Dr. Brian Goldman, host of White Coat, Black Art and The Dose, talked about third doses with Dr. Isaac Bogoch, an infectious disease specialist at University Health Network in Toronto and a member of Ontario's COVID-19 Vaccine Distribution Task Force.

Here is part of their conversation. 

What do you and other experts think of [the approach taken by Israel and the U.S.]? 

I think it's complicated. But if I was to summarize it in a few short sentences, I'd say, "Do we all need boosters right now?" The answer is, no, we don't. Will we all need boosters at some point in the future? The answer is yeah, we probably all will. And do some of us need boosters right now? The answer is also yes.

An expert review of evidence that was published in The Lancet this week concluded that the general population doesn't need booster doses right now. Why is that? 

We have to remember that these vaccines aren't really there to provide what we call sterilizing immunity. You can be ... fully vaccinated and still get COVID, and we've known that well before [the] delta [variant] even emerged. 

It's really helpful that it does reduce your risk of getting the infection. It just doesn't eliminate your risk of infection. The real heavy lifting of these vaccines is to convert a potentially lethal infection into a much more mild infection. 

And when we look at the data, it's pretty robust from multiple countries and multiple data sources demonstrating that, in general, they're about 90 per cent effective in preventing severe outcomes. Some data shows that it's a little higher, like 94, 95 per cent. Some data is a little lower. But in general, these vaccines do a very, very good job preventing severe illness. 

Do we all need boosters? No, we don't. Do some people need boosters? Yeah, some people don't mount the same degree of an immune response and are not going to have that same effectiveness. Those individuals should be getting boosters. 

Infectious disease specialist Dr. Isaac Bogoch says offering third doses to certain immunocompromised people is a "reasonable first step" to third COVID-19 vaccine doses. (Submitted by Isaac Bogoch)

Here in Canada, the National Advisory Committee on Immunization (NACI) made some recommendations on third doses last week. What were those? 

They basically defined who would be deemed immunocompromised. And they suggested that those individuals should get a third dose. 

If you want to dig a little deeper, it's basically people with various types of cancers who are on various types of chemotherapies. It's people with organ transplantation, and there's people who are on additional medications like biologic agents for underlying inflammatory conditions that can suppress the immune system.

What have the provinces been doing with these NACI recommendations? 

I think most provinces will probably not be too far from this, and that's kind of what we've seen throughout COVID. The provinces don't automatically just take NACI and copy and paste it, but it's usually pretty close.

And in addition to that, we're seeing provinces start to give third doses to those who also live in congregate care settings. It's also clear, and there's also emerging data, that frail elderly individuals, especially those in long-term care facilities, could benefit from a third dose.

Maybe moving forward, that would be expanded. But as of September 2021, I think that's a very reasonable first step. 

Do we have a clearer idea right now how long the immunity lasts from the COVID vaccines that are currently in use? 

I think it's pretty clear that they're good for at least six to eight months, probably longer. 

I think the real metric that matters is looking at the effectiveness against preventing severe illness, hospitalization and death and ICU stay. The whole goal, even from the beginning, was to convert a potentially lethal infection into the sniffles, not to eliminate this infection. 

And if the vaccines are continuing to really mitigate the severity of illness in the vast majority of people, then you don't have a global public health crisis anymore. You have a global nuisance. And that's a lot better. 

How worried should we be about breakthrough infections at the present time? 

I think if we start to see breakthrough infections resulting in significant hospitalizations and deaths and ICU stays, I would be worried. But we're not seeing that. We're just not. These vaccines currently are really holding up to the test of time. 

Some have suggested that we should wait until manufacturers can make a booster that takes into account the newer variants of concern. What do you think about that? 

We know that the virus has changed significantly since the earliest viruses emerged from Wuhan, China. And of course, there's different mutations along the way.

There will be a time where we'll need a booster. Why not get it at the appropriate time? Why not get a booster that's better suited to the virus that you're going to be exposed to, not the virus from over a year and a half ago? 

Are there any variants out there you think we might need a booster for in particular? 

The short answer is no. But a more nuanced answer is that it's not what we see that makes me nervous. It's what we don't see that makes me nervous. There's still the potential with unchecked viral transmission in many parts of the world that a variant will emerge that probably won't evade immunity that vaccines confer, but will just chip away at it. 

And really, this is why global vaccine equity is so important. We really have to get vaccines to every part of the world because it's the ethical and moral thing to do. And the other reason is it does curb the emergence of variants of concern, and it'll just end this pandemic faster. 


Written and produced by Rachel Sanders. Q&A has been edited and condensed for clarity.

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