AYESHA RASCOE, HOST:
Scientists say, if you've been infected with coronavirus and been vaccinated, then you have a very powerful immune system. They call it hybrid immunity or super immunity, and it could fight future variants of the virus. To help us understand what that is, we're joined now by Theodora Hatziioannou. She's a virologist and research associate professor at Rockefeller University. Welcome to the show.
THEODORA HATZIIOANNOU: Thank you. Thank you for having me.
RASCOE: So can you explain what hybrid immunity is, like, that I've read about some places? What are researchers referring to when they're talking about hybrid immunity?
HATZIIOANNOU: So the use of the word hybrid is - for lack of a better term, what they are referring to is the immunity that a person acquires after having been infected with SARS-CoV-2 and then vaccinated, essentially trying to describe that you have had two slightly different exposures to the antigen, one via infection and one via vaccination.
RASCOE: OK. And so when you've been infected by the actual virus and you're also vaccinated, does that somehow make you less likely to get it again? Because we're hearing about people getting it three and four times. Or is it only a certain type of person that gets this hybrid or super immunity?
HATZIIOANNOU: No, actually. Everyone - our studies and studies from a lot of other labs have shown that, if you have been infected and then vaccinated and actually vaccinated with a number of different vaccines, then the same effect is seen in your immune system. So your antibodies - you produce really good antibodies and that are also very broad. So they can, let's say, deal with the variants much better compared to other circumstances. So it's not a particular, let's say, characteristic of certain people. I would say we see it in a lot of people that, as I just mentioned, have received different types of vaccines. And unfortunately, when we talk about protection, a lot of people immediately associate protection with protection from getting infected.
RASCOE: Yes.
HATZIIOANNOU: But that's not necessarily the case. And I would also say, unfortunately, the vaccines and our pre-existing immunity doesn't seem to afford us a high level of protection against getting infected.
RASCOE: Is it possible, if you are unvaccinated, that you can get some sort of natural or have some sort of natural immunity to COVID? Has that been seen at all?
HATZIIOANNOU: So when you do get infected, you do develop immunity against the virus. And if you are infected, you will also develop antibodies, you will develop other responses. But that by itself, particularly if you've been infected just once, is not as good as being infected and then vaccinated. And the other study that actually recently came out shows that you don't actually have to get infected to get this really high level of memory B cells that produce these really good antibodies. Three doses of an mRNA vaccine produce a very similar effect.
RASCOE: What do you think about the state of immunity in the U.S. right now? Cases are rising and, you know, we see that in the numbers. We also can just see it anecdotally. Everywhere you turn, there's someone who has COVID these days.
HATZIIOANNOU: Yes, absolutely. And I think that's exactly what we're seeing. So if you look at how the omicron wave in particular played out in places like Hong Kong, where the vaccination coverage was not as good as one would hope, particularly in the older population, you see that it was actually pretty severe. And you don't see the same thing here. And it is because we - our immune system is no longer naive. It's not the first time we're seeing this virus. We have seen it before - not quite in this form but close enough for us to be able to have, apparently from the data, and at least so far, a pretty good level of immunity for most of us.
RASCOE: There is a concern out there that people are becoming complacent because maybe they've had COVID and they've been vaccinated. What do you tell those people about, like, what should their level of concern be as they're moving throughout the world and, you know, going about their daily lives?
HATZIIOANNOU: I would say patience for a little bit longer, at least until we can have a little bit more data, have the possibility to vaccinate all age groups that want to get vaccinated. And you don't have to be as draconian as you were before. But I always think - and it's my personal opinion - is that a mask is the least of all evil. You can still wear a mask in public places, particularly in places with - of mass transit and the theater or cinemas and things like that where a lot of people congregate in large numbers in enclosed spaces. Just wear a mask. It's actually extremely effective if you wear a good mask in preventing transmission.
RASCOE: Virologist Theodora Hatziioannou, thank you for joining us.
HATZIIOANNOU: Thank you for having me.
(SOUNDBITE OF ERNEST RANGLIN AND FLOYD LLOYD SEIVRIGHT'S "RAMOULIN VERSION") Transcript provided by NPR, Copyright NPR.
