IRA FLATOW: This is Science Friday. I’m Ira Flatow. It was announced this week that New York City will require proof of COVID-19 vaccination for some indoor activities like dining and exercise. It is the first city to announce this kind of policy. And this is all in an effort to get more people vaccinated as the Delta variant has shaken up efforts to curb the pandemic.

Spikes in cases are happening all around the country, just as kids are getting ready to get back into the classroom. And debates on masks are rearing their heads again. This is prompting lots of questions. Are we going to need booster shots? How much should we worry about breakthrough infections? And what on Earth has happened with the infection rates in the UK? They have plummeted.

Joining me today to help us break down these questions and more is my guest, Dr. Celine Gounder, infectious disease specialist and epidemiologist at NYU and Bellevue Hospital, and host of the Epidemic Podcast in New York City. Welcome back to the show, Dr. Gounder.

CELINE GOUNDER: It’s great to be here, Ira.

IRA FLATOW: Nice to have you. OK, let’s get right into this. Let’s talk the proof of vaccination New York will require for some activities. From a public health perspective, do you think this is going to encourage more people to get vaccinated?

CELINE GOUNDER: We certainly hope so. So this new system, what we’re calling Key to New York City Pass, we’re going to be requiring in New York City that people be vaccinated against COVID, have received at least one dose of vaccine, in order to go back to indoor dining, indoor fitness, indoor entertainment and performances, so the fun stuff that you would do in New York City. It’s not going to prevent people from going to work, or going to the drugstore, or getting food. But if you want to engage in New York City to its fullest and really enjoy all that the city has to offer, there is going to be a requirement starting mid-September that you be vaccinated.

IRA FLATOW: Vaccinations have been picking up back in the US. Is this because of concern for the Delta variant, do you think?

CELINE GOUNDER: Public health officials and other government officials are very concerned about what we’re seeing with the Delta variant. The Delta variant is different. It is at least twice as infectious or contagious as early strains of the virus.

And that means that one person who is infected today could go on to infect twice as many people as they might have infected if their infection had been early in the pandemic. And this is because people who get infected with the Delta variant have 1,000 times as high the level of virus in their nose and throat as they would have had with earlier strains of the virus. So there is just a lot more virus in their upper airways that they can spread around, not to mention that if you got more virus in your body, there is more virus to make you sick as well.

IRA FLATOW: That’s really interesting. It is shocking every time you hear about that 1,000 times figure. It’s amazing.

This week, Delta Airlines’ CEO said the company wasn’t planning to require vaccines for US flights, because COVID shots are not fully approved. What is the difference between the emergency approval we have now for the vaccines on the market versus full approval? Where does that get us, full approval?

CELINE GOUNDER: More time is the biggest difference. So to get the emergency use authorizations, the companies had to submit two months of follow-up data on participants in their late-phase clinical trials. And to be clear, that’s actually quite a lot of data.

There were tens of thousands of people in those phase-three clinical trials. And any time we’ve seen an adverse reaction, a side effect from a vaccine, any vaccine in the history of all vaccines going back to smallpox, those side effects have occurred in the first two months after vaccination. So that was a very sensible, logical cutoff to get emergency use authorization.

With full approval, companies have to submit six months of data. The FDA is currently reviewing tens of thousands of pages of data. And then they also have to do extra stuff like going to visit the manufacturing plants, making sure those are up to snuff. So there are some differences.

But we really do think these vaccines are safe and effective. 4 billion doses of vaccine have been given around the world, over 350 million here in the US. And we haven’t seen any real safety signals.

IRA FLATOW: Well, my question is, do you think that once these vaccines are fully approved, it’s going to be easier to mandate them? Do you think more people will be willing to get vaccinated once there is full approval?

CELINE GOUNDER: I think the real power of the FDA full approval is going to be around mandates. Now, I’ve spoken to a lot of public health legal experts about whether you can mandate even with just the emergency use authorization. And you can legally do so.

But I think many companies, state health departments, and others are waiting for that full FDA approval to give them additional legal cover. Do I think people will be convinced that the vaccines are safe because the FDA provides full approval? Based on surveys by the Kaiser Family Foundation, maybe. But from those same surveys, it also seems like people don’t really understand the distinction.

I mean, these are kind of technical regulatory distinctions. And having participated in focus groups around this question, my sense is, when people say they want the full approval or they want more data, it’s really just a polite way of saying, I don’t want to get vaccinated. It has very little to do with actual safety concerns.

IRA FLATOW: Yeah, that’s a very interesting point. I want to talk about the dramatic increase in infections we’ve seen this summer due to the Delta variant. I mean, last year at this time, infections went down. What’s the difference between this summer’s cases and last summer? Is it just that the Delta variant is so much more aggressive?

CELINE GOUNDER: I think it’s a combination of things. So first of all, the Delta variant is far, far more infectious than the earlier strains of the virus. So it does spread much more effectively from person to person.

But if you’ll remember, we did have a second wave last summer in the Southeast and other parts of the South across the country. And that’s really because the seasonality of their respiratory infections is different. If you think about it, when do people go indoors in different parts of the country? Well, in the South, it’s really hot and humid during the summer. And so it makes sense that you would see more respiratory virus transmission in the summer. And that’s precisely what we’re seeing, is that places like Florida, Louisiana, Arkansas, Missouri, places in the South, which also have low vaccination rates, we are seeing a big spike in Delta cases, hospitalizations, and deaths in those parts of the country.

IRA FLATOW: Yeah, that’s what it must be, because I’ve always been told that viruses are vulnerable to high temperatures. Certainly, above 90 degrees, they can’t survive very well. So I guess going indoors answers that question.

CELINE GOUNDER: Yeah, I think there is a lot that we still don’t fully understand about the seasonality of COVID. I think India was really unscathed for a long time and then had this massive surge a couple of months ago, much of that driven by the Delta variant. So we don’t fully understand this. But there is no question, when people are spending more time indoors, regardless of the time of year, that there is more transmission of this virus.

IRA FLATOW: I want to get to this question in Great Britain showing a mysterious drop in cases recently. They were expected to rise significantly. And they just sort of petered out. Do we know why that is?

CELINE GOUNDER: This is one of the many mysteries of COVID. And we’ve seen a similar pattern. India had this huge surge and then a very steep decline in cases. And we don’t entirely understand why that is. There are differences between the UK and India. The UK has vaccinated much more of its population. And India, they’ve barely really started vaccinating. So you can’t really attribute that to just vaccination.

Some people think it may be related to genetic differences in the innate immune system. So we have two main branches of the immune system. You have what we call the innate immune system and the adaptive immune system. So adaptive, it adapts. It evolves. It learns over time. And that’s where things like your antibodies come in.

But even before antibodies come into play, you have the innate immune system. So these are cells, chemicals, responses that will defend you against infection even before your body has really learned what that invader is. And we think there may be some genetic differences in that innate immunity that could potentially explain why we saw a big surge and then a steep fall.

IRA FLATOW: I want to move on to this question of a third dose of vaccine, because Israel recently started giving some citizens a third dose as a booster shot. Should we be taking cues from the Israelis?

CELINE GOUNDER: Well, and it’s not just Israel, Ira. You also have the UK, France, Germany, Hungary, Russia. There is country after country that’s been announcing this. The WHO has pleaded with the world that we really focus on vaccinating the unvaccinated before we give folks extra doses. And I really do agree with that. We get very, very good protection against severe disease, hospitalization, and death with our currently available vaccine regimens here in this country. And it’s really about optimizing your protection for the individual that you would give extra doses.

The couple groups in which I might consider an extra dose where there is good data to support that it would give them extra protection against severe disease, hospitalization, and death would be highly immunocompromised people, so people, for example, who’ve had a lung transplant or a kidney transplant, people who have HIV/AIDS, people who have certain cancers or on certain drugs for autoimmune disease, but that’s a very select group of people. The other couple of groups might be individuals over the age of 80 and folks living in nursing homes. But I really don’t think it’s the best use of our vaccine supply at this time to be optimizing individual protection against milder forms of the disease. And frankly, we’ll all be better protected if we focus on vaccinating the unvaccinated in this country than we will by getting individual extra protection with these additional doses.

IRA FLATOW: Yet on the other hand, I hear stories– and I’ve heard them personally– of some people quietly, almost secretly , getting third shots as boosters? Would you advise– I imagine you would not advise this.

CELINE GOUNDER: Well, now you have San Francisco General Hospital and San Francisco’s Department of Health, they have recently decided to allow some people to get extra doses of vaccine. I really don’t think this should be a free for all, number one. I think, number two, we really need to step back and think, what makes sense from a public health perspective, particularly when this is a scarce commodity and in limited supply?

And me as an individual– so I’ve gotten two doses of Pfizer. I recognize, well, maybe I could boost my immunity a little bit more by getting a third dose of Pfizer, but I am actually better protected, me individually, if all of those people who are currently not vaccinated in my community, if we vaccinate them. And so I think that really needs to be emphasized. That is the better protection even for you if you think about your own individual health.

IRA FLATOW: And there are some people who have gotten the Johnson & Johnson, the J&J vaccine, which is the one-shot deal, feeling that, well, you know, I’ve only got this one shot. It may not work. I’m going to go for the other two. And they’ve gone out and got vaccinated.

CELINE GOUNDER: Yeah, this is a bit of the story that’s happening in San Francisco where they’re giving extra doses. There is data that the Johnson & Johnson vaccine protects less well against infection than the Pfizer and Moderna vaccines. But when it comes to protecting against severe disease, hospitalization, and death, which is after all, why we vaccinate, the Johnson & Johnson vaccine remains quite good. And again, the very specific groups in which I might consider giving an extra dose would be highly immunosuppressed, people over the age of 80, and people in nursing homes.

IRA FLATOW: I know because you’ve heard these stories where German Chancellor Angela Merkel got an AstraZeneca dose and then a Moderna shot. And then our frequent Sci Fri virologist Angela Rasmussen got Johnson & Johnson and now a Pfizer two months later. What’s your take on mixing doses from different manufacturers?

CELINE GOUNDER: So the AstraZeneca vaccine is a two-dose vaccine. So Chancellor Angela Merkel, when she got a second dose, it’s not that she was getting an extra dose. She was mixing and matching vaccine types. And I think that’s an important thing to note here.

What we are seeing with these mix-and-match regimens– the fancy terminology for that is heterologous prime boost– is that you actually get an even better immune response when you mix and match than when you stick to the same type of vaccine for both doses. So I do think that is something we’re going to see more and more of in the future.

IRA FLATOW: This is Science Friday from WNYC Studios. In case you’re just joining us, we’re talking with Dr. Celine Gounder, an infectious disease specialist and epidemiologist at NYU and Bellevue Hospital, host of the Epidemic Podcast in New York City. Let’s continue talking about this, because there has been so much terrible news about the Delta variant lately. I’ve got a bit of a mind bender for you, something that I keep thinking about. And I’m going to run it past you. It may be kind of silly.

Could a variant develop that spreads as strongly as Delta but is harmless and outcompetes the dangerous variant in the body? We always talk about a villain variant. Could there be a white knight variant possible?

CELINE GOUNDER: There could. That’s certainly possible. It’s also possible that you could get something like Delta, but even more infectious, even more virulent and deadly, even more immune evading. It’s very difficult to predict how the virus will mutate over time. The only thing we can say with certainty is that, the way natural selection works is it will select for the virus that replicates most effectively and transmits most effectively from person to person.

IRA FLATOW: Let’s move on to schools ramping up to get started in the shadow of the Delta variant. Kids under 12 are still not able to be vaccinated. Is there, in your opinion, a safe way to go back to school in person?

CELINE GOUNDER: I think there is a lot that we’ve learned over the past year about how to make in-person schooling safe. Vaccination is certainly part of that for kids 12 and up, but we need to continue layering all of the other things that work. And so that includes not just having everybody who is eligible get vaccinated, so kids 12 and up, adults, but also continuing masking indoors. And we really do need to up our game with masking.

There is a lot that we’ve learned about which masks work better than others over time. Cloth masks do have value. But given that we don’t have the supply constraints we had early in the pandemic, I really would suggest switching to KN95 masks. Those are highly effective and are quite comfortable to wear during the entire day, so switching to that.

Improving ventilation– and again, that could just mean opening windows and doors. And then testing– we need to be testing on a regular basis so that people who are infected are not in the classroom. And we can really dramatically reduce risk and make the classroom a lot safer that way.

IRA FLATOW: One final question– we’ve also seen a lot of breakthrough cases. How concerned should we be about all these breakthroughs?

CELINE GOUNDER: I think the important news with the breakthrough infections is that they’re mild. Maybe people feel a little fluey, tired. They might have a mild fever, but they’re not ending up with low oxygen levels. They’re not ending up in the hospital. They’re not dying.

And I think oxygen levels is really– if you’re going to simplify this as much as possible, if your oxygen levels are not dropping, you are protected against severe COVID. And we’ve heard a lot of coverage of this Provincetown outbreak in Massachusetts over the past couple of weeks here where they saw a number of breakthrough infections. To me, that’s a success story.

That is what the world could look like post pandemic when most people are vaccinated. You know, I think around 75%-plus of people in that setting were vaccinated. And no one died. That is a huge win for the vaccines.

IRA FLATOW: That’s about all the time we have. We could keep going on. I want to thank you very much for taking the time to be with us today, Dr. Gounder.

CELINE GOUNDER: It’s my pleasure, Ira.

IRA FLATOW: Dr. Celine Gounder, infectious disease specialist and epidemiologist at NYU and Bellevue Hospital and host of the Epidemic Podcast in New York City.

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