Episode #49 - Can I get infected after vaccination?

13 August 2021 | Science conversation

Vismita Gupta-Smith

If you've been fully vaccinated, can you still get COVID-19? We're going to talk about breakthrough infections with Dr. Katherine O'Brien today. Hello and welcome to Science in 5, I'm Vismita Gupta-Smith. Welcome, Kate. My first question to you is, please explain breakthrough infections. How come people can still get COVID-19 even when they're fully vaccinated?

Dr Katherine O’Brien

The vaccines that we have against COVID are incredibly effective vaccines. And people have seen the results from the clinical trials of, you know, anywhere in the 80 percent range, 90 percent range of efficacy. But that doesn't mean that 100 percent of people, 100 percent of the time are going to be protected against disease. There is no vaccine that provides that level of protection for any disease. So we do expect in any vaccine program that there will be rare, but there will be cases of disease among people who were fully vaccinated and certainly among some people who were partially vaccinated. This doesn't mean that the vaccines aren't working. It doesn't mean that there's something wrong with the vaccines. What it does mean is that not everybody who receives vaccines has 100 percent protection. What we do want to really emphasize for people is that it's so important to get vaccinated because these vaccines are really effective and it gives you a really good chance of not developing disease.

Vismita Gupta-Smith

Kate, how frequent are breakthrough infections? And if you are fully vaccinated but happened to catch covid-19, what does that look like?

Dr Katherine O’Brien

So we're learning a couple of things about breakthrough infections, Vismita. The first is that the degree of severity of disease among people who have a breakthrough infection is less severe than the severity of disease among people who aren't vaccinated. So vaccines are operating in a couple of different ways. First, of course, they're preventing people from getting disease at all. And even when disease does occur among a person, people who are fully vaccinated, the severity of that disease is less.

The second question is about how often we're actually seeing breakthrough infections. We're monitoring this really carefully. And there's a couple of things I want to say about breakthrough infections. The first is that they are uncommon. And so this is not something that's happening in an unexpected way, but they don't happen equally among all different kinds of people. People who are at increased risk of disease, so people with frail immune systems, people who are in older age groups, they have a greater risk of having breakthrough disease than other people. So it's not an equal risk of breakthrough disease. The second point here is that we're seeing more cases of breakthrough disease, in part because people are stopping the other interventions that reduce the transmission of this virus. So when the virus starts to transmit at a greater and greater pace and with greater frequency, there's a lot more exposure that everybody has, including people who are vaccinated.

Vismita Gupta-Smith

So people may be wondering if they can still catch covid-19 even after being fully vaccinated and if they can still infect others, then why vaccinate?

Dr Katherine O’Brien

So this is a question that lots of people are asking. And I really want to emphasize that vaccines do a number of different things to protect you and to protect others.

So we've already talked about how the main function of vaccines is to protect you against getting disease. We've also talked about the fact that if you were to get disease, a rare event among vaccinated people, but it does occur that your disease will be less severe than it would have been if you weren't vaccinated. And the third thing that vaccines do is they reduce the transmission of the infection of the virus from one person to the next. And the way that vaccines do that is in a number of different ways. The first is they can protect you against getting infected at all. The second way that they work is if you become infected, you're actually shedding that virus for a shorter period of time than if you weren't vaccinated. And the third way that vaccines work is, again, if you happen to get infected, the amount of virus that you have in your nose, in the back of your throat that you are shedding and potentially transmitting to somebody is less of the virus. There's less density of the virus in you and so less risk that you transmit it to somebody else.

And what is so critical is interrupting transmission of this virus has to be “vaccines and” it has to be vaccines and all the other things that we're doing, especially while people are still in the process of getting vaccinated. So now really isn't the time for us to reduce those other interventions while we're living in communities that don't have substantial vaccination yet.

Vismita Gupta-Smith

Thank you, Kate. That was Science in 5, today. Until next time, then. Stay safe, stay healthy and stick with science.