MARY LOUISE KELLY, HOST:
Before omicron, the question was, will two shots of the COVID vaccine offer enough protection? Now, two months into the surge here in the U.S., the question has become, is a third shot, a booster, enough? Well, researchers in the U.K. have the first in-depth data addressing that question.
Here to explain their work is NPR global health correspondent Michaeleen Doucleff. Hey there.
MICHAELEEN DOUCLEFF, BYLINE: Hi, Mary Louise.
KELLY: So explain away. What have the researchers found?
DOUCLEFF: So the new data comes from researchers working with the British government, and they analyzed over 700,000 cases of omicron. And so far, they have long-term data just on people boosted with Pfizer. And what they found is that two weeks after the shot, protection against symptomatic infection is good. The booster cut your risk by about 70%, but that protection declines pretty quickly. About three months after your third shot, protection drops to about 50%, and researchers estimate it will continue to decline over time.
KELLY: Oh, wow. OK. So the protection that boosters provide would appear then to be pretty short term?
DOUCLEFF: Yes, against infection. Overall, it will likely last less than six months for most people.
KELLY: Wow. Which is exactly where we thought we were last year with the delta variant. That's what...
DOUCLEFF: That's right.
KELLY: ...Was prompting all the advice - get a booster, get a booster, get a booster.
DOUCLEFF: That's right. You know, immunologists I speak to say this is actually what they're expecting now with this vaccine really going forward.
KELLY: So why?
DOUCLEFF: Yeah. So I was talking to Jennifer Gommerman about this. She's at the University of Toronto. She said the primary way our bodies fight off an infection with SARS-CoV-2 is with antibodies, right? And your immune system makes a lot of antibodies right after you get the booster. But here's the dilemma.
JENNIFER GOMMERMAN: So when you're boosted, your antibody levels climb up, and then they diminish again with time, which is perfectly normal and expected. So we will see some protection with a boost against omicron, but that protection is going to wane.
DOUCLEFF: And, you know, the question with these vaccines has really been, how quickly would that protection drop off? And now we know, for infections, it's really on the timescale of months.
KELLY: I hear you emphasizing for infections. Do we know how well the boosters hold up with their protection against severe disease?
DOUCLEFF: Yeah. So this is much better news. Turns out, protection against severe disease doesn't depend so heavily on those antibodies. The vaccine triggers other parts of the immune system that keep an infection from getting out of control. And data from the U.K. indicates that protection against severe disease stays robust over time. The researchers found that after the third shot of Pfizer, protection against hospitalization starts out above 95% and remains high even after four months.
Now, I should point out that the study found that if you've had only two shots of any - really any of the vaccines, protection against hospitalization declines to 40% after six months. So that booster is important.
KELLY: OK, but where does all this leave us? So are we going to need to keep getting boosted every - I don't know - every three, four months?
DOUCLEFF: Yeah. Many scientists say, you know, that's really not practical or even effective. Preliminary data from Israel this week shows diminishing returns with a fourth shot. And scientists tell me we're getting to the point in the pandemic where stopping most infections is going to be impossible.
I was talking to Deepta Bhattacharya about this. He's at the University of Arizona. He says the focus may need to shift to making sure everyone is protected against severe disease.
DEEPTA BHATTACHARYA: Could we get to a point where, you know, the public health recommendations are shots maybe once a year? Yeah, I do think so. I think that's fairly likely. You know, whether people absolutely need it or not to prevent severe disease each year, we'll have to wait for the data.
DOUCLEFF: He says, you know, this yearly shot should be updated - versions of the vaccine that could offer that type of protection against future variants as well.
KELLY: All righty (ph). Thank you for the update, Michaeleen.
DOUCLEFF: Thank you, Mary Louise.
KELLY: That's NPR global health correspondent Michaeleen Doucleff.
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