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Tanya Lewis: Hi, and welcome to COVID, Quickly, a Scientific American podcast series.

Josh Fischman: This is your fast-track update on the COVID pandemic. We bring you up to speed on the science behind the most urgent questions about the virus and the disease. We demystify the research and help you understand what it really means.

Lewis: I’m Tanya Lewis.

Fischman: I’m Josh Fischman.

Lewis: And we’re Scientific American’s senior health editors. Today,  we’ll talk about how vaccines boost immunity even if you’ve already been infected… 

Fischman: … and how to handle going back to the office, even though COVID is still around.

Lewis: Many unvaccinated people believe that if you got COVID once, you’re totally protected against getting it again. But that’s not true. Can you explain?

Fischman: You’re talking about the idea of natural immunity, that an early infection prevents another one. It turns out that isn’t the best protection you can get. What seems to be better is something that scientists are calling “hybrid immunity.” That’s a natural infection plus a full course of vaccines. Three recent studies support this idea.

Now, a previous infection does help. A paper just published in the journal Lancet Infectious Diseases looked at people in Sweden who were infected once. They had a lower risk of another infection, when compared with folks who hadn’t ever been infected or folks who hadn’t been vaccinated.

But here’s where it gets interesting. Add vaccination on top of that early infection, and it improved protection by 50 percent. It also kept that protection going strong for another six months.

That dovetails with a long-term study in England, which tracked people for more than a year. It appeared in the New England Journal of Medicine. Early infection did prevent 80 percent of second infections that would otherwise be expected. That’s pretty good. But adding vaccines improved that protection more, to nearly 100 percent. 

Finally, a study in Brazil found that people who’d been infected, and then got 2 doses of vaccines, avoided 65 percent of the new infections that you’d normally expect, and 80 percent of severe COVID cases. So infection alone does something, but adding vaccines does a lot more.

All this brings up the issue of Omicron. I wonder, Tanya, if an infection with the original Omicron, BA.1, prevents you from getting  BA.2, the sub-variant that’s circulating now?

Lewis: That’s a great question. In a recent story, SciAm contributor Charlie Schmidt reports that early studies suggest reinfection with BA.2 after BA.1 is possible, but rare. “If you were infected with BA.1, then you’re probably well protected from BA.2,” Stephen Griffin, a virologist at the University of Leeds School of Medicine in England, told Charlie. But that protection may not be complete, Griffin said.

Countries that had big BA.1 peaks, like South Africa, haven’t seen a big BA.2 peak so far. Then again, the U.K. had a big BA.1 surge, and still saw a notable peak in BA.2 infections several months later. But that could be more to do with the fact that it dropped all COVID restrictions, so people who had avoided getting infected in the previous wave might’ve gotten sick later.

We’re already seeing an uptick in infections in parts of the U.S., especially in the Northeast. Whether that will lead to another surge or just a small bump remains to be seen. The good news is, many people will have some immunity from infection, vaccination, or both.

Fischman: So our company just announced it’s reopening the office. Everyone’s expected to show up. And with COVID still around, I’m not super-comfortable with crowds. Are you?

Lewis: Not especially. I’ve been pretty careful throughout the pandemic, avoiding most indoor places except for essential ones like the grocery store, and wearing an N95 or KN95 mask whenever I’m indoors. So the idea of going back to the office regularly, especially without a mask mandate, has me a little nervous.

Fischman: Aren’t you vaccinated and boosted, though?

Lewis: I’m not super concerned about getting very sick myself. But I do worry about spreading the virus to others who are more vulnerable. I actually have an immunocompromised family member I visit from time to time. Plus there’s the risk of long COVID. But I’m probably going to go into the office a couple days a week and just wear my N95. What about you?

Fischman: Yeah, I’m with you on the masks. People who work retail, in grocery stores and restaurants, wear them because they deal with a stream of different people all day. So I’ll do that too.

I also want to keep an eye on community spread. The CDC has a tracker for this, called “COVID-19 Community Levels.” You can Google it. It looks at both new cases and hospitalizations by country, and uses those to describe areas as low, medium, or high spread. 

Lewis: So, how do you plan to use that info?

Fischman: If my area goes into medium or high, I’m going to use a mask even more often. But it’s just weird, to look at stats showing that cases are starting to rise and then hop on a crowded train to go to a crowded office. Isn’t it?

Lewis: Yes, it is unnerving. Even though MY risk of getting severely ill with COVID is fairly low, that doesn’t mean I want to get it if I can help it, especially given we may be entering another surge. But does the CDC tracker miss some important info, Josh?

Fischman: True. That tracker is also too wishy-washy about when to wear a mask in “medium” risk areas.

Lewis: Right. And according to the CDC, Manhattan is already considered medium risk. For now, I’ll keep using my toolbox of precautions. In addition to wearing a good mask, I’ll continue to keep my distance from people on the train when possible, and avoid crowded areas of the office. 

Fischman: What do you think of our place? Does it have good airflow? 

Lewis: Our office doesn’t have windows you can open, but it does have a decent MERV filtration system. But even with these precautions, there’s still some risk, and you can’t help but feel a little anxious, right?

Fischman: Anxiety is OK. I mean, this virus has killed 1 million Americans in two years. Now we seem to be in a world filled with spikes and dips. We do know a lot more about how to keep ourselves safer today. If we all act on that knowledge–like doing some of the things you’re doing–maybe I and a lot of other people might start to feel kind of comfortable. 

Lewis: Now you’re up to speed. Thanks for joining us. Our show is edited by Tulika Bose.

Fischman: Come back in two weeks for the next episode of COVID, Quickly! And check out SciAm.com for updated and in-depth COVID news.

[The above text is a transcript of this podcast.]

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