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One year into the COVID-19 pandemic, vaccines are being deployed and administered around the world – with vaccine development, manufacturing and distribution all taking place at record-breaking speed.

But many Canadians continue to have questions about the different vaccines and how they work, particularly as the country races to inoculate citizens amid an increase in infections due to SARS-CoV-2 variants. 

Omar F. Khan, an immunoengineering expert and assistant professor at the Institute of Biomedical Engineering in the ������Ƶ’s Faculty of Applied Science & Engineering, runs a lab that designs nanotechnology devices that can deliver RNA technology to cells for better disease treatment.

Khan recently spoke to U of T Engineering writer Liz Do about several common concerns and questions around COVID-19 vaccines.

There are four approved vaccines in Canada. How are they different and how do they work?

Two are mRNA vaccines – Pfizer-BioNTech and Moderna – and two are viral vector vaccines: Johnson & Johnson and AstraZeneca. They are different methods of delivering an antigen.

An antigen is a unique protein that is used to sensitize the immune system to a pathogen. This unique antigen is only found on the pathogen and nowhere else in your body. Once the immune system is sensitized to it, the immune system then goes on to make antibodies. Antibodies are specialized protein complexes that float around in your blood and if they ever recognize the antigen, they stick to it. That “sticking” sets off a cascade of signals and the rest of the immune system converges and destroys the pathogen connected to the antigen.

The Pfizer-BioNTech and Moderna vaccines contain a piece of genetic information in the form of messenger RNA, or mRNA. This molecule is separate from DNA, so they don’t intermix. The mRNA molecule is an instruction set that your body can use to make the antigen.

The viral vector vaccines use a modified virus – not the virus that causes COVID-19, a different one – that has been changed so that instead of carrying instructions to make more of itself, it just carries instructions to make the antigen for the COVID-19 virus.

These vaccines were developed when there was one version of the virus. Now there are variants – how did this come about?

Because we’ve had so many cases of COVID-19, these viruses kept on replicating in people. Every time a virus replicates, there is an opportunity for a mistake to happen – this is a mutation. Most mutations are not favourable (to the virus), but some enable the virus to survive and spread more effectively, and so become a favourable evolutionary event. In this case, a variant emerges that outruns the original version because it can spread more easily and make more copies.

Do we know how effective the vaccines are against new COVID-19 variants?

The antigen that we’re using as part of the vaccine is called a spike protein, which we hope is relatively invariant in that it shouldn’t change too much. So, with these vaccines, we’ve trained the immune system to recognize an earlier version of the spike protein. If the variant has a slightly different version, then the fidelity isn’t quite there.

One way we can overcome this difference is to have a very high immune response by overwhelming the variant virus with antibodies. Booster shots can help maintain a high level of antibodies in your blood and is the reasoning behind the recommendation for a second shot.

What this all ends up meaning: These vaccines can no longer completely prevent disease. However, they can still reduce the severity of disease. We are in the middle of a very dynamic pandemic, where the virus keeps changing.

What this means for the person receiving the vaccine is that you have to be more cognizant of what “efficacy” means. Here, efficacy means a reduction in the severity of disease.

Why is there a public health push to get everyone vaccinated if we’re not completely stopping COVID-19?

There are several reasons. Mass vaccination can slow down the viral replication in the population. That leads to fewer variants, and our vaccines stay more effective. We are preventing the severity of the disease, which means less hospitalization and fewer patients in intensive care. Hence, we do not overwhelm the health-care system. I think the major confusion is that the vaccines are primarily preventing severe disease, and not necessarily completely preventing disease.

Does it matter which vaccine you get?

It doesn’t matter. The goal is to stop viral replication and the creation of new variants. All of these vaccines have shown, through clinical trials, that they will reduce the severity of disease. Get whatever you can get, because we don’t want to be responsible for creating a variant that is even more pathogenic. Let’s all try to fight this.

Some have expressed concerns of health side effects from getting the vaccine. We’ve seen in Europe the suspension of the AstraZeneca vaccine due to reports of blood clots, for example.

It’s good to be concerned and good to ask questions. But let’s help people understand why these things are happening.

Vaccines are a very special case of health-care technology. There’s a special burden on the regulations for vaccines that says, “If you give this to a healthy person and they become sick, we need to figure out if they became sick because of your vaccine, or because people become sick from an unrelated reason” and to decouple the two.

The AstraZeneca vaccine has been widely distributed around the world and administered to millions of people, particularly in the U.K. Of the people vaccinated there, they looked at these potential side effects and the rate at which they were occurring in order to determine if there’s a link.

So when the U.K. did this investigation, they found that the rate of blood clots happening in people was not different than the rate at which it happened in the overall public. Other countries, such as in France and Spain, want to make sure they are making the right call out of an abundance of caution – and that’s understandable and important to be resolved.

These safety procedures are in fact normal; it’s just that the awareness has been amplified because these protocols are under a big magnifying glass.

When do you think Canadians will see a return to something approaching pre-pandemic life, given the rise of variant infections?

If we look at the rate of which vaccines are being shipped, how quickly people can be vaccinated, but then also factoring in how long it takes your body to develop immunity, I think we are looking at 2022. By the time we have enough vaccines to vaccinate all Canadians, we’re already pushing into the fall.

How will mRNA technology change the treatment of diseases and vaccine development going forward?

This is a mosaic of technologies working together. We saw the different rates at which vaccines were developed, manufactured, distributed – not to mention the challenges with temperature-control distribution logistics. These are all important elements that are part of the ecosystem of pathogen preparedness.

I would say that of the more traditional vaccine technologies versus the newer technologies, I don’t think there’s necessarily a silver bullet that will supplant the other. But what this has shown is that we are fortunate to have many more new options and tools that improve vaccine accessibility globally, and hopefully prevent this from happening again.