ARI SHAPIRO, HOST:

Although kids are much less likely than adults to get seriously ill from COVID-19, pediatricians are reporting a worrying trend - more children are being hospitalized with the coronavirus than at any point during the pandemic. And as kids go back to school, doctors fear things could get worse, especially since the vaccine is not currently authorized for kids under 12. Dr. Roberta DeBiasi is head of pediatric infectious diseases at Children's National Hospital here in Washington, D.C.

Welcome to ALL THINGS CONSIDERED.

ROBERTA DEBIASI: Thanks, Ari.

SHAPIRO: Tell us about the difference between what you saw among children with COVID-19 early in the pandemic and what you're seeing now with the delta variant.

DEBIASI: Well, we've always seen a rate of hospitalization in children, even at the earlier surges of this disease. But I think what's being appreciated now is that since the delta variant is causing so much more sheer volume of infections and cases, that same percentage is reflected as a larger number of children that are ending up in the hospital. Now, we have had at Children's over 3,000 kids that we've taken care of with COVID since the beginning of this pandemic. And in this last surge, we are now again filling up our hospital isolation unit beds with children who are sick and have to be hospitalized.

SHAPIRO: So it sounds like you're saying children are the same proportion of hospitalizations compared to adults as before, it's just that because the delta variant is so much more contagious and kids under 12 are not vaccinated that you're seeing a greater number of them.

DEBIASI: That is right. And, you know, if we look at the American Academy of Pediatrics and Children's Hospital Association data, which has really been a very good source of information every two weeks since the beginning of this, children are still somewhere between 12- to 15% of all the cases of COVID and still are about 3- to 4% of all the hospitalizations. And we have not seen a huge change in that, even with this delta variant.

But again, if you have a larger number of cases overall and you apply that percentage, you're going to see children hospitalized. And that's really the most important take home for families is that there's nothing particularly more dangerous about the delta variant for children, but it has always remained a danger. And what we're seeing is that the children that are hospitalized are, for the most part - and adults as well are, for the most part, people that are not vaccinated, whether that's because they've chosen not to be vaccinated or if they are just in an age group that has not yet had access.

SHAPIRO: And when you look at things like long-term consequences from COVID-19 or some of the more severe but rare impacts - like, I understand you've been studying multisystem inflammatory syndrome of children or MIS-C, which is rare but serious - are you seeing the same pattern where the raw numbers might be higher but the percentages are more or less what they were, or does it seem like the delta variant might be more likely to cause significant impacts even for kids?

DEBIASI: These are all great questions. For - regarding MIS-C, we've had 165 cases at Children's. It always follows four to six weeks after a surge in COVID cases, and we're not yet at that point for delta, so we have not yet had a delta-associated MIS-C surge. We're certainly, you know, keeping very close track of that. And if it's going to happen, we expect it in the next two to four weeks because we're just seeing our surge in the delta cases, as I just mentioned.

SHAPIRO: Yeah.

DEBIASI: Your question about long-term effects, this is really so important in adults but really even more of an unknown in children. And we've just embarked on a six-year study that we'll be following as many as 2,000 children with COVID or MIS-C over three years each. And we'll be looking very - in a very detailed and systematic way at their heart function, their lung function, their mental health, their quality of life and then also establishing a biorepository of specimens and working with scientists to look at both antibody responses and also genetic susceptibility for these long-term effects.

SHAPIRO: OK, so a lot of questions we still don't have answers to. As students are returning to the classroom for the new school year, what kinds of precautions do you want to see schools put in place, especially for younger unvaccinated kids?

DEBIASI: Well, it makes a lot of sense to use the things that we know decreased transmission in prior waves. They're even more important now because delta is so contagious. So anything that can be done to increase masking, distancing, aeration, hand hygiene - all of those things still apply. Delta is very contagious, even in those that have received vaccine. That's a very important point for people to know. The vaccine is incredibly effective at preventing severe disease, hospitalization and death, but it is not effective in preventing actual breakthrough infection or ability to infect others, so we need to use all those measures.

SHAPIRO: Which means even vaccinated parents might want to be cautious around their unvaccinated kids, it sounds like.

DEBIASI: Absolutely.

SHAPIRO: All right, that's Dr. Roberta DeBiasi. She is head of pediatric infectious diseases at Children's National Hospital here in Washington, D.C.

Thanks, as always, for your time.

DEBIASI: Thank you so much. Transcript provided by NPR, Copyright NPR.