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Should I mix and match my COVID booster with my initial vaccine? A doctor weighs in


Eleven months ago, December 2020, the U.S. had just kicked off its mass vaccination campaign. Looking ahead to this winter, we are in a very different place. Nearly 70% of Americans ages 12 and up are fully vaccinated. And this time, the push is for booster shots. The FDA has now expanded authorization for the Pfizer and Moderna boosters, saying that anyone 18 and older who wants them can get them. A panel of experts advising the CDC made similar recommendations today. And this evening, CDC Director Rochelle Walensky signed off on boosters for all. But it does prompt a question. If you are facing a choice, which booster should you get? And is it worth mixing and matching? We're going to put those questions to infectious disease expert Dr. Celine Gounder of New York University. My co-host Mary Louise Kelly interviewed her earlier today.


There is some nuance in the CDC recommendations today. They say people ages 50 and up should get the booster versus people ages 18 to 50 may get the booster. What are your thoughts on that? Is it optional for those under age 50?

CELINE GOUNDER: Well, to be clear, even among the age 50, there are those who may. So if you have no risk factors, the recommendation is still may get a booster. And for the over age 50 who do have underlying medical conditions, it is should receive a booster. And at the end of today's meeting, there was some debate. Should we just make it should for everyone who's over age 50? - because the vast majority of them probably do have an underlying medical condition, whether or not it is diagnosed or has been diagnosed.

KELLY: Well - and that leaves me confused and the whole...

GOUNDER: (Laughter).

KELLY: The whole point of having this new guidance was to try to get some of the confusion and nuance out of it. Is this new guidance still too nuanced? Should they have just gone for it? Look; everybody just get a booster. What's the harm?

GOUNDER: Well, I think the big takeaway is if you're 18 and up - so if you're an adult in this country - you want a booster, you can get a booster. I think there are some nuances in terms of who should, who may. Some of this will continue to be ironed out as we get more data. But if you are 18 and over and you want a booster, you can get a booster, assuming Dr. Walensky, the director of the CDC, signs off on today's vote.

KELLY: To the question I just raised about what's the harm of getting one, there is an ethical question in here. I'm remembering a few months back the director general of the World Health Organization tweeting that it was unconscionable that some countries are offering boosters, those countries including the U.S., while so many others in the world haven't had any vaccine at all. Is a booster for someone in this country coming at the expense of an unvaccinated person abroad?

GOUNDER: Well, for logistical reasons, it's very difficult for us to send whatever doses we have of vaccine here in the United States overseas. So I don't think the individual who decides they want to go and get a booster should feel guilty. I do think there are larger, systemic issues that do need to be addressed because at a global level, you know, it is a zero-sum game. You do have scarcity of vaccines. There is not enough vaccines for many countries around the world. But that's really for government officials to be sorting out, not for the average person who's trying to decide whether they want to get a booster or not.

KELLY: To the questions about mixing and matching, if I got one vaccine initially - I got Moderna. Should I get a Moderna booster shot? Can I get a Pfizer? Does it matter?

GOUNDER: So that's already been ruled on, which is basically you can get whatever you want as your booster. By and large, based on what we're seeing from the data, people are pretty much sticking - if they got with Moderna, they get a Moderna booster. If they got Pfizer, they got a Pfizer - they're getting a Pfizer booster. The only one we're seeing a bit of mixing and matching is with people who got the Johnson & Johnson to start with who are now getting...


GOUNDER: Sorry. My dog's in the background.

KELLY: I see your dog has a view on this.


GOUNDER: They want a booster, too. You know, I think by and large, where we're seeing some mixing and matching is with people who got J&J where they may get Moderna or Pfizer as their booster.

KELLY: Yeah. I mean, so we can get - we can mix and match. Should we mix and match? I have seen some data pointing to - that it might help boost your immune system if you got one vaccine to start with and then you switch to a different one.

GOUNDER: Yeah, I mean, that's a theoretical possibility. What we are seeing is probably more related to dose. So in the mix and match study, the recipients got higher doses with the Moderna boost, but in fact, what they're getting in the real world, so to speak, is a half-dose for the booster. So I really don't think you're going to see significant differences among the three different brands. I would say, you know, get whatever's easiest for you to get if you're going to get a booster.

KELLY: Are we starting to see any significant differences in terms of the effectiveness of the three vaccines that have been offered to Americans - Pfizer, Moderna, Johnson & Johnson? We've been told they all work. You should all get vaccinated. But there is some data coming out showing that one is maybe a little bit more protective than the others.

GOUNDER: Yeah. So it's clear now that the Johnson & Johnson vaccine should be considered a two-dose vaccine, kind of like Moderna and Pfizer already were. So that's pretty clear. With respect to Moderna versus Pfizer, Moderna does seem to be slightly more effective and more durable. And again, this may relate to the fact that there's just a higher dose that you get with the Moderna vaccine of that mRNA vaccine than you get with the Pfizer vaccine.

KELLY: And when you say some of the data pointing Moderna may be both more effective and more durable, just to emphasize that that is saying - both that it maybe offers slightly greater protection and that that protection lasts longer.

GOUNDER: That's right. That's right. And I would say still, you know, these are very small differences. You know, I got the Pfizer vaccine myself as one of the, you know, first to be eligible as a frontline care provider. I got my first dose of vaccine in December of last year, and all we had was Pfizer back then. And I really don't feel that I am any less - significantly less protected than somebody who got Moderna at some point later.

KELLY: Last question - any tips for Thanksgiving in terms of assessing risk versus reward when it comes to get-togethers over the holiday?

GOUNDER: (Laughter) Well, I think ideally everyone would be vaccinated. And the other things that we recommend - so think of it like winter layers. You know, you wear your sweater and your jacket and your mittens and your hat. You know, similarly combine other things, too. So, you know, if you're in a place that allows, do as much outdoors as you can or open doors and windows. Buy a HEPA air filtration unit if you can and put that in the dining room or other places where people are sitting together. And then finally rapid tests. They are too expensive still for most people, but if you're able to afford them, test on the day of, on the morning of Thanksgiving. If you're negative, you can enjoy.

KELLY: That is Dr. Celine Gounder, epidemiologist at NYU, also practicing at the Bellevue Hospital in New York City. Thank you.

GOUNDER: My pleasure. Transcript provided by NPR, Copyright NPR.

Mary Louise Kelly is a co-host of All Things Considered, NPR's award-winning afternoon newsmagazine.
Ashley Westerman is a producer who occasionally directs the show. Since joining the staff in June 2015, she has produced a variety of stories including a coal mine closing near her hometown, the 2016 Republican National Convention, and the Rohingya refugee crisis in southern Bangladesh. She is also an occasional reporter for Morning Edition, and, where she has contributed reports on both domestic and international news.
Christopher Intagliata is an editor at All Things Considered, where he writes news and edits interviews with politicians, musicians, restaurant owners, scientists and many of the other voices heard on the air.