COVID-19 cases are trending upwards across the country. In Massachusetts, where vaccination rates are relatively high, cases are still on the rise — and a cluster in Provincetown among mostly vaccinated individuals caused the town to issue a new mask advisory Monday. Tufts Medical Center epidemiologist Dr. Shira Doron spoke with Arun Rath on GBH’s All Things Considered about where thing stand in the Commonweath and the nation.

Arun Rath: It probably makes sense to start with today's news out of Provincetown. The town is putting its indoor mask advisory back in place after more than 100 new COVID cases popped up after the July Fourth holiday. What do you make of that uptick and the response?

Shira Doron: Well, the outbreak is unexpected. It's not what we've been seeing. There's quite a bit of transmission there reported between vaccinated individuals. And really, what we've seen so far, has been that, certainly, breakthrough cases occur in vaccinated individuals — usually they have mild symptoms, which we do believe to be the case here — but usually they don't transmit to others, so the fact that there are so many cases — 132 reported — that a good proportion of them are vaccinated and that it appears that there was transmission among them is unusual. And so it makes sense for health authorities there to take some swift and rather aggressive action, at least for the moment, to try to control the outbreak, and then continue to study what might have happened there, because there's still so much we don't know.

Rath: Interesting. So that uptick of 100 cases is as unusual as it sounds, that's sort of why the response is what it is.

Doron: Yes, we really haven't seen anything quite like this yet.

Rath: Are you concerned that we will start to see other incidents like this?

Doron: I hope not. I hope that this was, you know, an anomaly that was probably related to the fact that the delta variant is so very contagious that some people who harbor it have very, very high viral loads in the respiratory tract. The fact that it was a holiday weekend, very crowded bars and nightclubs, some rain that drove people inside more than usual, and that perhaps all of those things came together this one time to cause this outbreak. Now, if this turns out to be an outbreak where most of the vaccinated people — or hopefully all of them — had mild infections, then, really, I think the vaccine did what it was intended to do, which was to prevent people from getting really sick, and we could go back to the way things were a couple of weeks ago where we were celebrating the the high efficacy of the vaccine at protecting us and allowing us to live our pre-pandemic type of life.

Rath: And, on that point, at the numbers we're seeing nationally and what we're hearing is that the uptick in cases is happening among the unvaccinated. President Joe Biden said that this is now a pandemic of the unvaccinated. Does that square with what we're observing here in Massachusetts?

Doron: Yes. I mean, you really have to ask yourself: what are we trying to prevent here? We're trying to prevent serious illness, hospitalization, death, long COVID. If we had found out in November that the vaccine didn't protect us against mild infection at all and only prevented hospitalization and death, we still would have cheered from the rooftops. If the vaccine allows some people to have common cold-type symptoms, that's okay, we just want to make sure that it protects people against severe disease.

Rath: And at the same time, I'm hoping you can give us a sense of risk here, because we hear about breakthrough COVID cases where people who have been vaccinated are still coming down with the virus, and I think the rates we're seeing that, of those who are hospitalized, you know, 97 or 98% are unvaccinated. But, still, how concerned should one be about the 2% — who are vaccinated — who still seem to end up in the hospital?

Doron: Well, you know, the vaccines aren't perfect. And often when somebody does end up in the hospital for COVID after being vaccinated, that's somebody who you might have predicted would not respond as well to the vaccine — in other words, people who are severely immunocompromised. Now, the CDC has said that some of the numbers that they're reporting as COVID hospitalizations in fully vaccinated individuals are actually people who happen to be in the hospital for other things and test positive, since we are, for the most part, still testing everyone who is admitted to the hospital. So that's good news. The vaccines are working really, really well right now, even against the delta variant.

Rath: So we should still feel good. Those of us who are fully vaccinated but still feel fairly protected, feel very protected, from the sounds of it.

Doron: Yes. But it is a matter of personal risk tolerance. Cases are up. The delta variant is so contagious, I would not blame anybody who's fully vaccinated who wants to wear a mask in crowded indoor settings — that's a perfectly reasonable thing to do — but I also don't tell people that they must do that or that they should do that.

Rath: One of the things that we've talked about, both in terms of how the disease is affected people but also the vaccinations, there have been various racial disparities. And we know there's been a lag in certain groups getting vaccinated. Are we also seeing that those groups, again, are more likely to come down with with COVID in this bit of an uptick?

Doron: Yeah, that's a great question. I have not seen the latest data on race and ethnicity in terms of who is ending up in the hospital right now. The focus has been on the fact that younger age groups are less well vaccinated right now, and that we are indeed seeing younger age groups presenting to the hospital with severe disease.

Rath: And tell us a bit more about what you are seeing at Tufts. You know, when you're getting new COVID cases, where are they coming from, the people, ages, all that?

Doron: Yeah, so we are not seeing fully vaccinated people end up in the hospital at all, though we are seeing some vaccine breakthrough infections in our outpatient settings. So that's really consistent with what you were just saying in terms of the numbers. And we are seeing quite a few people on that younger age spectrum, and I think that's really related to the fact that the disease is so contagious and the younger folks — in Massachusetts and throughout the country — are less protected by vaccination.

Rath: And we had heard from epidemiologists that, come autumn, there was likely to be an uptick by, you know, the nature of how these viruses tend to work, but is that inevitable — is some sort of an uptick inevitable, or is there a way in which we can avoid that by having these higher vaccination rates?

Doron: If I've learned one thing about COVID-19, it's that we can never predict what it's going to do next. You know, about a year ago, we were talking about mathematical models all the time, and you've noticed we talk about them a lot less now — and that's because they always proved to be wrong. This virus has never followed the textbook. Just look at Texas unmasking everybody in early March and still seeing plummeting rates — until the delta variant came along. So delta is a game changer. I was expecting to see cases rise in the fall and winter due to people spending more time indoors and whatever else it is that causes viruses to be seasonal, which I think we don't fully understand, and yet here we are in July with the cases already ticking up, unfortunately, which is quite a disappointment.

Rath: Before we go, we just have a minute left. But I wanted to ask you: you know, we're hearing a lot more concern from parents who have kids who are under the age of 12, because obviously they can't get vaccinated. Heading into the second half of the summer and into the fall, any advice or thoughts for parents in terms of keeping their kids safe?

Doron: Yeah, I am hearing a lot of that concern as well, and I do want to remind people that, although the delta variant is very contagious — it is equally contagious for all — it doesn't have a predilection for children, none of the variants have. And our children are still at very, very low risk for severe disease, hospitalization and death. You know, England just re-analyzed all of its COVID death data amongst children under 18, and when you really look at them and try to determine who is in the hospital — or who died due to COVID — versus with COVID. They actually came up with only 25. I shouldn't say only, because every death is tragic, but 25 deaths throughout the entire pandemic. And I think it would be good for the U.S. to re-analyze that data as well. But we if we can get our cases back down again with better vaccination of adults, children will be protected by virtue of low case rates here in Massachusetts with the success of our vaccination campaign. And so I hope that by the time school starts, perhaps cases will be better under control. And by virtue of the rarity of infection, children will be protected.

Rath: Dr. Doron, it is so helpful to to have you to give us some context to it, to all of this. Thank you so much, again.

Doron: You're so welcome.