Episode #31 - Vaccines, variants & doses

 

26 March 2021 | Science conversation

Vismita Gupta-Smith

Hello and welcome to Science in 5, WHO's conversations in science. I'm Vismita Gupta-Smith and we are continuing our conversation about vaccines, answering questions about vaccines today is Dr Katherine O'Brien. Welcome, Kate.

Dr Katherine O’Brien

Thank you. It's nice to be with you again today. 

Vismita Gupta-Smith

Kate, the first question I wanted to ask you was: getting vaccinated - does that prevent infection? And what if we get Covid after getting vaccinated? Can we still infect others?

Dr Katherine O'Brien

So this is a great question Vismita. What we know about the vaccines, is that they're really effective against disease. They're really effective at protecting us from getting especially severe disease and hospitalization. The second question we have, though, is do they prevent against infection. Of the early evidence that we have, it does look like these vaccines are not only protective against getting symptoms, actually developing disease, but they do seem to also prevent getting infected in your upper respiratory tract. 

It looks like they might, even if you do get infected, also reduce for how long you're infected. And it also looks in very early data that when you're infected in your respiratory tract, you might have less of the virus in your respiratory tract than if you're not vaccinated. And each of those things would reduce the likelihood that you would transmit that virus to someone else. So these are really interesting results that are starting to come out. But I really want to emphasize how early they are. 

That means that we only have one or two studies. We also don't have these results for each of the vaccines that are now out there. And as everybody knows, there are a number of vaccines that are being used around the world. So this is the reason why we keep emphasizing that as vaccines are rolling out, as we're in this early phase of the use of vaccines, people need to continue to wear masks and continue the other interventions that are keeping us safe and reducing transmission. 

Vismita Gupta-Smith

Kate, another question that we get often is about vaccines and variants. Once we are vaccinated, does that protect us against the variants? And also, does it mean that a new variant would impact us less? What about all the variants that are coming out, future variants? Do vaccines protect us from these variants? 

Dr Katherine O'Brien

From what we do know about the vaccines that are broadly used around the world is that for most of the variants, the vaccines continue to be effective. They may not be as effective as they are against the non variants, but they nevertheless still have substantial effectiveness against disease. You asked also about other variants that are coming up. We should expect that we're going to continue to see variants pop up and emerge. It's what viruses do. And the vaccine manufacturers are clearly going to and already adapting vaccines to try to make them as best they can be against a range of variants as we learn more about how those variants are interacting with the vaccines. The most important thing is, this is one of the really big reasons why even if you're vaccinated it's important to keep wearing a mask. We don't have the evidence for each of the vaccines, for each of the variants, nor for variants that will come up in the future about the degree to which the vaccines are protective against you getting infected. They may protect you against getting sick, but you could then go on and transmit to somebody else and they could get sick if they're not vaccinated. 

Vismita Gupta-Smith

Another question we are getting nowadays is what if I've already had Covid? Do I only need one dose of the vaccine now? 

Dr Katherine O'Brien

We still recommend that if you've had Covid disease, you should get a full course of the vaccines that are out there and available to you. So if it's a vaccine that requires two doses, you should get the two doses. We certainly have seen evidence that a single dose of vaccine, especially in people who have had Covid disease in the past, gives a really strong antibody response. And that's really good news. It shows that the vaccine is boosting the immunity that has developed as a result of the illness that they had. 

But the reason that we recommend that you go ahead and get the a full course of the vaccine is twofold. First of all, we don't have the evidence yet about whether or not a single dose following disease would be fully protective or equally protective against the variants that are now out there. And we also don't know about the duration of protection. So without evidence to really assure people that a single dose of a vaccine that would normally be given in two doses is going to give you durability of protection and is going to give that height of protection that would really provide the optimum protection against variants, we're recommending still that you go ahead and get both doses of vaccine. 

Vismita Gupta-Smith

Thank you, Kate. That was Science in 5 today. So don't forget to share this information and be the source of scientific, evidence-based information. Until next time then. Stay safe, stay healthy and stick with science.