A MARTINEZ, HOST:
There's a new study from the National Institutes of Health that suggests those who got the Johnson & Johnson shot could mix things up when getting a booster. Joining us now to explain it all is NPR health correspondent Rob Stein. Rob, a lot of people thinking about getting boosters probably assume they'd get the same vaccine as the original dose. I'm right there along with them. What did the study find?
ROB STEIN, BYLINE: Yes - well, the bottom line is if you got either the Moderna or Pfizer vaccine, it looks like getting either of those vaccines for your booster will pump up your immune system about equally. So it doesn't really matter if you got Moderna or Pfizer for your first shots. Go with either of those for your booster. But it seems like a different story if you're one of the 15 million people in this country who got the Johnson & Johnson vaccine to start. It looks like it could be much better to get either the Moderna or Pfizer vaccine for your booster, not just another J&J shot.
I talked about this with Dr. Monica Gandhi at the University of California San Francisco.
MONICA GANDHI: Getting a Moderna or Pfizer first, really doesn't matter what mRNA vaccine you get next. But if you have had a Johnson & Johnson, this really shows us that the best vaccine to get next is an mRNA vaccine, either Moderna or Pfizer.
STEIN: This comes from this eagerly awaited study from the NIH. Researchers gave 458 volunteers getting boosters every possible combination of vaccines and found that crucial antibodies, known as neutralizing antibodies, shot up 10 to 20 times higher if Johnson & Johnson people got a Moderna or Pfizer booster instead of another J&J shot.
MARTINEZ: Wow. Sounds pretty significant. Why would that be?
STEIN: Well, this study wasn't designed to specifically answer that question. But there's a couple of things going on here. First of all, you know, the one-shot J&J vaccine has never generated as strong protection as the other vaccines. And another possibility is that an entirely different kind of vaccine may just rev up the immune system a lot more than just giving another one of the same kinds of vaccine.
Here's Monica Gandhi again.
GANDHI: And you raise a more diverse and active immune response by getting this mixture of vaccine.
STEIN: Now, I should point out that some of the researchers involved in the study are stressing that it wasn't designed to compare different boosters. And while doctors think higher antibody levels probably translate into less illness, this study didn't actually show that. Also, other parts of the immune system stimulated by the J&J vaccine may also be important. So they say the bottom line is the results provide evidence all three vaccines could be helpful boosters. And for its part, Johnson & Johnson is standing by its vaccine as a booster and is asking the FDA to authorize that.
MARTINEZ: And this comes just as the FDA is starting a two-day hearing to consider the request to...
MARTINEZ: ...Authorize boosters with the Moderna and J&J vaccines. How does that figure into what's going on?
STEIN: Well, it certainly could complicate things. You know, the FDA's already given the go-ahead to Pfizer boosters for millions of people. And Moderna and J&J are arguing that their booster should get authorized for similar reasons. More breakthrough infections are occurring in the face of the delta variant. And they say boosters of their shots will help make sure more vaccinated people don't get really sick or die. But there's a lot of skepticism about whether people in this country really need extra shots when the vaccines are still working really well. And, you know, most of the world hasn't gotten vaccinated at all. So it's unclear how the FDA will square these new results, especially with J&J's request. And so it could be another pretty intense debate.
MARTINEZ: And the next big question is vaccines for the kiddos. So when we're going to get news about that?
STEIN: Yeah, yeah. That's right. That's the big question on the minds of millions of parents. When can young kids - you know, those ages 5 to 11 - get vaccinated? The same FDA advisers will take up that question on October 26, and the CDC will then weigh in on that on the first week of November. So if both of them sign off on Pfizer's request to authorize the first vaccine for young kids, those shots could finally start coming, you know, maybe before Thanksgiving.
MARTINEZ: All right. That's NPR health correspondent, Rob Stein. Rob, thanks.
STEIN: You're welcome. Transcript provided by NPR, Copyright NPR.