07/02/2021

How Alarmed Should You Be About The Delta Variant?

17:26 minutes

a crowd of people at sunset mostly wearing masks
Credit: Shutterstock

This story is a part of Science Friday’s coverage on the novel coronavirus, the agent of the disease COVID-19. Listen to experts discuss the spread, outbreak response, and treatment.


It’s been six months since the first variant of COVID-19 raised alarm bells around the world. Now, a particular variant seems to be spreading rapidly: the Delta variant, first identified in India, and now the dominant strain in many countries, including the United Kingdom. In the United States, the variant makes up more than 20 percent of cases.

South Africa, Australia, Germany, and other countries are re-imposing limits on travel and daily life. And Israel, where more than 60 percent of people are vaccinated, has reinstated mask requirements. In fact, the World Health Organization is recommending that all fully vaccinated people continue to wear masks as this variant spreads.

What does that mean for you? Virologist Angela Rasmussen helps take the temperature of the Delta variant and other COVID-19 news—including promising results on the Novavax vaccine, clues about long-lasting immunity from Pfizer’s mRNA shot, and more.


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Segment Guests

Angela Rasmussen

Angela Rasmussen is a research scientist at VIDO-InterVac, the University of Saskatchewan’s vaccine research institute in Saskatoon, Saskatchewan.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. It’s been six months since the first variant of COVID-19 raised alarm bells around the world. Now, one variant above all others seems to be spreading rapidly. I’m talking about the delta variant first identified in India.

And then now has spread to more than 80 countries. South Africa, Australia, Germany, and other countries are reimposing limits on travel and daily life. And Israel, where more than 60% of people are vaccinated, has reinstated mask requirements. In fact, the World Health Organization is recommending that all fully vaccinated people continue to wear masks. And Los Angeles County advised everyone to wear masks indoors in public places even if fully vaccinated.

What does that mean for you? Here to help us take the temperature of the delta variant and other COVID-19 news is Angela Rasmussen, research scientist VIDO-InterVac, the University of Saskatchewan’s Vaccine Research Institute in Saskatoon, Saskatchewan. Welcome back.

ANGELA RASMUSSEN: Thanks for having me back, Ira.

IRA FLATOW: We’ve talked about the variants before, but this delta variant is really making the rounds. I mean the dominant variant of the virus in many countries, 20% of cases in the US, that variant. Do we know why it’s so contagious?

ANGELA RASMUSSEN: So we really don’t. It could be that people are remaining contagious for a longer period of time. It could be that the virus is better at finding its receptor, ACE2 and infecting cells, that’s called infectivity. It could be that the virus is just making more virus and shedding more infectious virus, thereby increasing the odds that you will be infected if you’re exposed to somebody who is infected as well.

So we really don’t know. But to me the epidemiology data is quite clear that this virus does spread quite easily, particularly among unvaccinated or partially vaccinated people. And for that reason, it is rightfully a big concern.

IRA FLATOW: And we still don’t know if it’s more likely to cause serious illness.

ANGELA RASMUSSEN: That’s something that I think is very, very difficult to try to figure out with epidemiologic data. Human populations and populations of unvaccinated or partially vaccinated people are going to be different in every community and in every place where the delta variant might be spreading. And if you end up seeing an increase in people going to the hospital relative to other variants, it could be just that different people are getting infected. People with other risk factors.

But because it’s infecting more people it appears that it is more pathogenic or virulent. So that’s something that still remains to be seen and there are studies trying to get to the bottom of this. But to me, the take home message for everybody is really clear. You should get fully vaccinated because full vaccination does provide strong protection against the delta variants.

IRA FLATOW: And I think that’s what we’re seeing in Israel, where the vaccination rates are high. There are a significant number of their cases in vaccinated people, but they’re not serious illnesses.

ANGELA RASMUSSEN: That’s exactly right. So this is one thing that’s really frustrating about some of the media coverage about this. People talk about all these breakthrough infections happening in fully vaccinated people. But they don’t mention that the people who are actually in the hospital are largely unvaccinated or partially vaccinated people.

The people who are fully vaccinated may test positive for the virus, they may have transient abortive infections. And this actually normally happens with many other vaccines that are very, very effective. But the vaccines are holding their own against the delta variant. And that is that they are protecting people, even people with breakthrough infections from becoming seriously ill, from going to the hospital, and from dying.

IRA FLATOW: So what should people do? They’ve heard the WHO. Should I keep my mask on, how should I make that decision?

ANGELA RASMUSSEN: Well, you think this is something that we’re all sick of wearing masks. And that can’t be underestimated, masks can be uncomfortable, especially in hot weather. But masks are a relatively easy non pharmaceutical intervention to apply. Certainly they’re are a lot better than closing down businesses or telling people to stay home.

Many of the breakthrough infections in vaccinated people, in a few cases there has been evidence of secondary transmission. Now, this is probably much lower again, than would occur in unvaccinated people. But to just protect yourself, as well as try to protect your community around you, especially those people who aren’t yet fully vaccinated, a mask is a relatively low cost way to do that and just add one more layer of protection.

IRA FLATOW: And on top of all of this, the delta variant has its own variant. Which is being called delta plus. Something to keep an eye on or to be worried about?

ANGELA RASMUSSEN: I mean it’s definitely something to watch because delta plus has an additional mutation that’s been characterized in some other variants. We don’t know however, the effect that this is having in delta itself. We don’t know if it’s going to be any worse or potentially even any better or just the same as delta. So it’s one to watch, but there’s no reason to get extra worried about delta plus.

IRA FLATOW: And that’s a good point. To move on to my next point, because we’re now seeing studies and results by Moderna and Pfizer that their vaccines are found to be effective for much longer periods of time, and against these variants.

ANGELA RASMUSSEN: So there’s a couple studies there to unpack. And in one, I think we have very clear data that the Moderna and Pfizer mRNA vaccines are holding up really well against all of the variants. So people who’ve been fully vaccinated, you’re two weeks passed your second shot, have really exceptional protection against both infection, but importantly against severe disease from any of the variants that we’ve seen so far.

In terms of the long-lasting immunity. That was a very small study but it was a very exciting study to that followed people after they’d been vaccinated and actually took samples from their lymph nodes. And the lymph nodes are where a lot of the business of the immune system happens. That’s where your B cells will differentiate into specialized B cells that are really good at producing antibodies for a really long time, that’s where immunological memory is generated.

So this study looked in 14 people over time in their lymph nodes. And what it found was a type of B cell called germinal center B cells, which are really important for immunological memory. And for many other vaccines, those cells tend to persist for about four to eight weeks. In this study people still gad those germinal center B cells going strong after 15 weeks.

In addition to that, they also had type of B cell called a plasma blast that is a B cell that’s really basically a neutralizing antibody factory. So that really bodes well for long term protective immunity. If these cells are in people’s lymph nodes, being active long after the vaccine has been cleared, that does suggest that people will have long-lasting immunity. But unfortunately, the only way to determine how protective that immunity is in the real world is really just to wait and see. So we do need to have more research.

IRA FLATOW: Do we think at this point that people might require booster shots?

ANGELA RASMUSSEN: I think one of the things that’s going to be really helpful in that is defining what are called correlates of protection, which we still haven’t been able to do. Normally, this is something that happens in the course of a phase three clinical trial or just after a vaccine has been approved and released on the market. And that’s basically finding a convenient laboratory measure to assess whether or not the vaccine is going to be protective.

Because these vaccines were put onto the market before we had a chance to do those long term studies– and I think that was the right move, because obviously it was beneficial to get the vaccines as soon as possible. Now that a lot of people have been vaccinated, we will be able to do that and certainly, so far, it looks like neutralizing antibodies unsurprisingly, may be a good correlative protection. Although that research is still in progress.

So once we do have that, we should be able to know by testing if people’s immunity is starting to wane. The other way we would potentially identify that is if a lot of vaccinated people start getting COVID, particularly if they start getting symptomatic COVID and ending up in the hospital.

But fortunately, that’s not happening in vaccinated people right now with any of the variants that are circulating, including delta. So it doesn’t appear that right now, anyways, we do need to start thinking about boosters for all of the vaccines.

IRA FLATOW: We’ll have to keep an eye on that is what you’re saying. On a more complicated note, both the mRNA vaccines, I’m talking about Pfizer and Moderna, have been linked to a heart inflammation condition called myocarditis. The CDC has updated its factsheets about both vaccines to note that this is a small risk but also increases after the second dose. So Angela how serious is this side effect?

ANGELA RASMUSSEN: Well, this is something that seems to predominantly be affecting younger people who are getting the mRNA vaccines. And so far myocarditis can be serious, there have been a few cases that have ended up in the hospital. And to put this in perspective– I mean everybody’s going to have their own risk tolerance, everybody is going to have their own risk benefit analysis.

But in my mind, the risk of having severe myocarditis that needs to be hospitalized is much higher from having COVID than it is from getting the vaccines. So my risk benefit analysis would say that the risk of myocarditis from the vaccine is much lower than the risk of myocarditis from COVID or the many other serious potential side effects of having COVID. So I would still get the vaccine and recommend it for my kids too.

IRA FLATOW: Let’s move on to another vaccine that has some promising clinical test results, I’m talking about the Novavax. It’s a much more traditional vaccine than the mRNA ones, right? I mean it’s akin to the whooping cough vaccine. Could that make more people feel safe taking it, knowing that?

ANGELA RASMUSSEN: I think it really could. And the Novavax clinical trial results were incredibly encouraging, it does seem to be a very effective vaccine as well. It’s what’s called a protein subunit vaccine, so it is actually making the spike protein before it goes into your arm. What’s new about this is it actually uses a different protein expression system that’s derived from moth cells, they can make quite a bit of protein.

They’ve coupled it with a compound that stimulates your immune system and makes vaccine responses more effective. It really does appear that it works very, very well. I think for a lot of people who are unsure about the mRNA or the adenovirus vector technology, might feel more comfortable getting a protein subunit vaccine. Because as you pointed out, these have been used for the acellular pertussis vaccine, they’ve been used for the hepatitis B vaccine.

Most people are familiar enough with those vaccine technologies that they might feel comfortable taking that. Protein subunit vaccines are very temperature stable, and they’re easy to transport. So I think the Novavax vaccine is also going to be really huge for vaccinating other parts of the world, where it may be more difficult to bring the mRNA vaccines in particular.

IRA FLATOW: And Novavax has pledged more than a billion doses to the Global COVAX program.

ANGELA RASMUSSEN: Yes, and that’s going to be absolutely crucial. Because with the clotting issues that have come up, these are still very rare side effects with Johnson & Johnson with AstraZeneca. A lot of people in other countries have rightly wondered if they’re getting the short end of the stick. Why aren’t we getting these great mRNA vaccines that wealthier countries are getting?

And I think that having a very effective vaccine that is not on an adenoviruses vector platform will do a lot for global vaccine confidence, as well as just for getting the vaccine out to the rest of the globe. And it’s hard to see this from the US, where now we have so many vaccines that vaccines are expiring on freezer shelves, that there are parts of the world where people have not been vaccinated against COVID. They have not gotten access to those vaccines, including health care workers, including high risk people. So I think that it’s absolutely crucial to get this vaccine out as soon as possible because a pandemic is by definition a global public health crisis. We need to make sure that we’re vaccinating the world.

IRA FLATOW: This is Science Friday from WNYC Studios. I want to wade into a discussion that’s been happening about where the virus came from. We mentioned a few weeks ago that President Biden had ordered an investigation into the origins of COVID-19. And now we’re getting some push back against the idea that this was created intentionally in a laboratory someplace in China. Push back coming from some very well-known scientists.

ANGELA RASMUSSEN: Yeah. So this has been a really contentious topic and it’s really unfortunate. A lot of times what people do need to understand is that most of the time, it takes a long time to figure out where a virus came from. In many cases, even though we know where some viruses come from, we still haven’t actually proved it.

And Ebola is a great example of that. We know that it’s transmitted by bats, we know that it’s carried by bats, they’re its natural reservoir, but we don’t even really know what species. And we’ve never isolated live Ebola virus from a bat, we’ve only just started basically isolating sequences of Ebola viruses from bats. Ebola came onto our radar in 1976, so it’s been around for almost 50 years. And we still don’t have a solid answer, a definitive answer on that virus’s origin. But nobody thinks it came from a lab, obviously.

So the situation with COVID or with SARS coronavirus 2 is that the first outbreak that was observed was in Wuhan, China, where there is a major virology institute, where they were working on bat coronaviruses. Then we know that these sarbecoviruses, that’s the sub genus that SARS coronavirus 2 is in, the SARS-like coronaviruses, is normally in the wild in bats.

We also know that it can infect a number of different intermediate species. And SARS coronavirus 2 is also quite promiscuous in terms of the number of other species that it can infect. So there’s a lot of different possibilities, including the possibility that it came out of a lab accident. I think everybody does agree that analyzing the genome of this virus suggests that it wasn’t a biological weapon.

In my opinion, I think that a natural origin remains the most likely. But it’s true that we have not ruled out the possibility that it could have come from a lab. But I think one point that I’d like to make here, Ira, is that people have been talking about this lately as though these are equivalent possibilities, nature or the lab. In my opinion as a virologist, looking at the genome, looking at the number of other species that this virus can infect, the weight of the evidence points toward an animal natural origin.

And one of the reasons for that, that we can look at and see in real time, is that this virus was not properly adapted to human hosts. That suggests that it was a very, very recent spillover event. That still doesn’t exclude again, lab exposure, but that does suggest that this virus was in no way pre adapted or passaged to make it more effective as a human pathogen.

And the evidence for that is right in front of our eyes it’s the variance the reason why variants are emerging is because this virus is spread through the human population to the point that now it is beginning to evolve and adapt to us. If this virus was pre adapted, or if it was already being passaged through human cells or being developed into a human pathogen. For research purposes, not even necessarily for malicious purposes, we would see those variants in the first viruses that were circulating.

But we have not. So I think that it is important to investigate all potential origin hypotheses, and as I said, none of them have been ruled out. But in my opinion, again, I think that the natural origin hypothesis is by far the most likely.

IRA FLATOW: Well I think that’s a good place to stop. You have certainly filled us in on a lot of questions we’ve all been having in our own minds. Thank you, Angela.

ANGELA RASMUSSEN: It’s always a pleasure, Ira.

IRA FLATOW: Dr. Angela Rasmussen, a research scientist at VIDO InterVac, that’s the University of Saskatchewan’s Vaccine Research Institute in Saskatoon.

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