STEVE INSKEEP, HOST:
OK. Let's review a few things that Dr. Fauci just said. He said the vaccine is the beginning of the end game. He then said it would take inoculating 50% or so of Americans to have a serious impact, maybe 75% or 80% of Americans to really stop the virus. So we're talking about vaccinating 250 million people or so. Vaccinating that many involves more than one vaccine, so this news is important.
The Food and Drug Administration has released its evaluation of a second COVID-19 vaccine, which is made by Moderna. The FDA is expected to grant the company emergency use authorization for the vaccine maybe later this week. And in the meantime, NPR science correspondent Joe Palca has been reviewing the latest FDA evaluation. Hey there, Joe.
JOE PALCA, BYLINE: Hello, Steve.
INSKEEP: What do you see?
PALCA: Well, yes, this vaccine, I think, is very similar to the BioNTech-Pfizer one - 94% effective overall at preventing COVID disease, slightly less than 94% percent in older people, but also appeared to be effective in that group. And the shot is not a pleasant experience for most people. The evaluation of the data that Moderna provided, the FDA said that, you know, almost 91% of people had pain where they got injections and fatigue and fever. But these are considered annoying rather than debilitating. And the alternative is, of course, being exposed to a deadly disease.
INSKEEP: Yeah. Yeah, something that can affect you for weeks or months or even kill you. Now, when we say 94% effective, I guess we should just remember tens of thousands of people got the vaccine, tens of thousands of people were studied who didn't get the vaccine. And there were a few cases, but almost no cases, that came up among the people who got the vaccine. Are there any surprises in this evaluation, though?
PALCA: Not really. And even though 10,000 sounds like a large number, the difference between 10,000 or 20,000 or 40,000 and 40 million is pretty great. So there may be things that turn up when the vaccine is rolled out to a huge population that we just don't see now. But based on what people know - and that's the only criteria they can use right now - there doesn't seem to be a problem.
INSKEEP: Now, you also said there, Joe, that it seems about like the findings of the other vaccine. How do they compare based on the data that you do have?
PALCA: Well, the comparison is just a little bit tricky because the Moderna vaccine is given once - twice but 28 days apart, and the Pfizer-BioNTech one is 21 days apart. But in general, they seemed equally effective at preventing disease, as I said, maybe a little less effective in older people. But there did seem to be slightly more of these local reactions and maybe even fatigue - some of the more general reactions, or fever, after the second dose in the Moderna vaccine. But that's something that experts are warning (ph).
You know, there's a panel that's going to meet later this week, the vaccine advisory panel, that the FDA has convened. They're going to be talking about this and trying to see whether they think any of these things require special attention. It doesn't seem like it now.
INSKEEP: Can you explain just a bit of the science here? How is it that each of these vaccines helps the body fight off a virus?
PALCA: Well, these vaccines are very similar in their design. Both inject a small amount of genetic material taken from the virus that causes someone who gets that genetic material to make a protein that the virus makes. And that protein prompts a - an immune reaction in the person that prepares them. If the real virus ever were to come along, their immune system would say, hey, I've seen this before, and will mount the kind of reaction that will prevent illness.
INSKEEP: OK. And suppose approval does come through later this week, as is now expected, what happens right after that?
PALCA: Well, Moderna says it's ready to ship out 20 million doses of the vaccine. That's enough for 10 million people. And after that, they say there's a order for 100 million on the books.
INSKEEP: Wow. Joe, thanks so much.
PALCA: You're welcome.
INSKEEP: NPR's Joe Palca.
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