Welcome to your first class. We will begin class with a casual conversation. Our discussion today is about the corona virus vaccine. I want you to introduce a topic from you lecture to me. Please listen to the audio clip and read the transcript simultaneously.

STEVE INSKEEP, HOST:

We've had two kinds of pandemic news lately - stories about the horrifying increase in cases across this country and stories about rapid progress with a vaccine. Today, we have an update on one of the two vaccines announced in recent days. Pfizer and its partner BioNTech announced an effective vaccine last week based on tests that were not then complete. Now they say they've finished the study, and the results are still very good. NPR's Joe Palca is with us. Joe, good morning.

JOE PALCA, BYLINE: Good morning, Steve.

INSKEEP: What did the findings add to what was known?

PALCA: Well, as you say, last week was an interim analysis, and this is what's called - this trial is what's called an event-driven trial. It doesn't go for a fixed amount of time. It goes until they reach a predetermined number of events, and in this case, an event is a case of COVID. And they pick the target because they want to pick a number that will give you something that they can be statistically confident in that the results are real and not a fluke. And they didn't know how much COVID was out there, so they thought it might take six months to get to the target, which was 164, but the trial started at the end of July, and now it's concluded - so quite a bit faster.

INSKEEP: Wow. Kind of sad, actually - cases are so widespread you can test for a vaccine quickly. You're telling me there's a group of people, they waited a while to see if people with the vaccine got COVID, how many of them did and waited a while and see if people with a placebo got COVID and how many of them did. So what are the numbers?

PALCA: Yeah. That's exactly right. Something like 43,000-plus got shots. Half got two shots of the vaccine. Half got two shots of a placebo. There were 170 cases total of COVID among all the participants, 162 cases in the placebo group and eight in the vaccine group. So that kind of tells you that the vaccine is protecting people and the placebo, obviously, is not.

INSKEEP: Yeah. Yeah. The vaccine - not absolutely perfect but very, very good compared to the placebo. How exactly, though, did they define their terms here? When we talk about people getting a case of COVID-19, is this people who got really sick?

PALCA: Yeah. Well, in this case, all they said to begin with was, we want you to have at least one symptom - that would be a cough or sneeze or a persistent or runny nose or something like that - and a confirmed test of COVID. Initially, at least, the company said that they hadn't seen any severe cases, but now they're saying there were 10 severe cases, nine in the placebo group and one in the vaccinated group. And I have to say here, Steve, that if - a lot of scientists say if you can protect people from getting a mild case of the disease, you're probably also protecting them from getting a severe case, so that's the conclusion here.

INSKEEP: OK. So how do all of these very positive-sounding results compare with the results on the other vaccine from Moderna that we heard about the other day?

PALCA: Yeah. They're remarkably similar. These two vaccines are actually very similar in their design. There're some differences in some of the packaging, and by packaging, I mean the molecular packaging. But they use the same principle, a bit of messenger RNA, mRNA, and the results are almost, you know, to this point, identical. The difference, apparently, at this point is that the Pfizer vaccine is a little more finicky for storage. You have to keep it in ultra-cold freezers.

INSKEEP: What happens next?

PALCA: Well, as you say, they apply to the Food and Drug Administration for emergency use authorization. The FDA wanted to see some safety data. So far, things look very safe. They only saw fatigue among the study participants. So if the FDA grants the vaccine EUA, it could be going out to people by the end of the year.

INSKEEP: NPR's Joe Palca, thanks so much.

PALCA: You betcha (ph).