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Understanding Breakthrough COVID Infections


Coronavirus cases are again surging across this country. While the CDC reports that over 97% of the people hospitalized with new cases had not been vaccinated, there is a growing number of something called breakthrough infections or infections among vaccinated people. In the first two weeks of July in Provincetown, Mass. more than 250 people contracted COVID. And officials there say the vast majority of those people had been vaccinated. To learn more about what these breakthrough infections mean, we've reached Dr. Cassandre Pierre. She is an instructor of medicine at the Boston University School of Medicine, and she's with us now. Hello.

CASSANDRA PIERRE: Hello. Great to be here.

GARCIA-NAVARRO: What's your reaction to the Provincetown outbreak and seeing this number of breakthrough infections in one place?

PIERRE: I have a sense of disappointment but also inevitability. We know that the vaccines that are authorized at this moment are incredibly effective against COVID-19, including the Delta variants. And we expected that as more and more people moved to indoor settings and experienced a mix of unvaccinated and vaccinated individuals in one space, that we would start to see an increase in number of infections, primarily among unvaccinated individuals but with vaccinated individuals, as well. However, I at least anticipated more of this happening in the fall. The conditions that happened in Provincetown over July Fourth weekend, I think, unfortunately were set up for this kind of situation. Lots and lots of people forced to crowd into indoor spaces due to the inclement weather. Lots of people engaging in close conversations from mixed households. And then you also have the fact that the Delta variant is highly transmissible.

GARCIA-NAVARRO: Talk me through why this is happening. I'm assuming, I guess, that vaccinated people think they're less likely to have COVID, and then they're not getting tested, and they're not quarantining appropriately. What is going on?

PIERRE: We know that with our vaccines, many individuals have a sense that they can't get sick. And so there's probably some disinhibition in some of the activities that they may be engaging with. Being on vacation, as well, also adds to that sense of disinhibition. And what we're also seeing is a sense that people may have symptoms like a runny nose, headache, things that they may ascribe to seasonal allergies or another one of the viral infections we're seeing rise in this country and may disregard the need to test themselves. The other thing I want to note is this Delta variant - early reports are saying that it's going to be a shorter time from the time to exposure to the time to infection to the time to exposing other people and being infectious. And so that makes it more important for people to take their symptoms seriously because we want to really catch this at the very beginning.

GARCIA-NAVARRO: But do we know yet if vaccinated people transmit the virus to others?

PIERRE: We haven't had a good sense of whether individuals who are vaccinated can transmit or cause secondary infections. But we are having a little bit - there is a bit more information, including, probably, this cluster of infections in P Town itself that is showing that, although incredibly rare, individuals who are fully vaccinated can indeed transmit to other individuals.

GARCIA-NAVARRO: So right now, the CDC is not telling people who have been vaccinated to return to mask wearing. I'm curious, in your own family, what are you doing? I mean, I have a unvaccinated child who is not eligible for vaccination yet. What should we be doing to protect them?

PIERRE: We need to look at our own context and our own communities. For example, in my community, we still have very low COVID-19 transmissions. But if I'm going to go to another area where I see a rising number of infections, we are masking in our indoor settings. And were I to go to an area where there is a lot more travel happening, a lot more vacationing, unfortunately, again, you're going to see conditions where COVID outbreaks can occur. And so in those situations, best to remain in outdoor locations, you know, with children, for example - and I have children, as well - sticking to those outdoor areas as much as possible and when going into indoor areas, wearing masks as much as possible. I think that's what this particular incident has taught us.

GARCIA-NAVARRO: The NFL just announced it's going to penalize teams if there are outbreaks because a player has not been vaccinated. Italy and France are imposing limits on where unvaccinated people can go - no movies, dining out. I know this is controversial, but medically speaking, do you think there's a place for more restrictions or consequences for those who have chosen not to be vaccinated?

PIERRE: I find it hard to think about consequences for not being vaccinated, because we know that there has been a lot of misinformation that many of us who do not have access to trusted medical advisors are privy to. And so we need to do a little more due diligence. I know we feel like we've done a lot, but many people are tuning into different streams of media and also are surrounded by friends and family that might reinforce ideas about the vaccines that are not true. And so retribution against those who are unvaccinated makes me very uncomfortable. However, thinking about prevention and limiting amounts of individuals who are unvaccinated in spaces where people are indoors and crowded and unable potentially to be fully masked, for example, at an athletic game, does seem to make more sense to me. So more about prevention and less about punitive action.

GARCIA-NAVARRO: That's Dr Cassandra Pierre, an instructor of medicine at the Boston University School of Medicine. Thank you very much.

PIERRE: Thank you. Transcript provided by NPR, Copyright NPR.

Mara Liasson is a national political correspondent for NPR. Her reports can be heard regularly on NPR's award-winning newsmagazine programs Morning Edition and All Things Considered. Liasson provides extensive coverage of politics and policy from Washington, DC — focusing on the White House and Congress — and also reports on political trends beyond the Beltway.
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