MARY LOUISE KELLY, HOST:

And, boy, is it rare to get to say the words coronavirus and good news in the same sentence. But today from the pharmaceutical upstart Moderna came word that its vaccine is nearly 95% effective. Last week Pfizer announced similarly promising results, a vaccine that's more than 90% effective. The FDA benchmark for approval is 50%. Moderna's chief medical officer is Tal Zaks. He is with us now.

Welcome.

TAL ZAKS: Good to be with you this evening.

KELLY: I need to give all the caveats up front here. Widespread distribution of this vaccine, any vaccine, is likely months away. And, of course, the coronavirus is ravaging the country as we speak. There are all kinds of challenges ahead. But for today, congratulations. What is the mood today inside Moderna?

ZAKS: Thank you, Mary Louise. I think it's a combination of elation and relief. We have been optimistic now for weeks and months that our vaccine should be protective because of the high levels of neutralizing antibodies that we've seen. We were delighted to see Pfizer's news last week. I think that clearly bodes well. And to have a point estimate of, you know, almost 95% of the ability to protect people from this disease - and it's worth noting that we were very transparent with our results. We described the subgroups. We had 11 subjects with severe disease there, and all 11 cases occurred only on the people who got placebo. None of the vaccinated individuals had severe disease. I think it is really reassuring to us the proof of efficacy as demonstrated in this trial and ability now to project our ability to prevent disease for people is now real.

KELLY: I do have to dig in on one of the challenges, which is production - just having enough. Moderna has said you can make 20 million doses by the end of the year. And I understand everybody needs to take two, which means that's 10 million people who might be covered, which means the vast majority of Americans are not going to get it, at least not right away. What do you need to ramp up production?

ZAKS: Well, we've already been ramping up production. And so we're going full steam ahead. We have been for months. We are on track to deliver to the U.S. government the first hundred million doses, and the U.S. government has optioned to purchase more. It's a matter, then, of distribution. We're able to have a supply chain. Our vaccine requires a typical storage temperature of minus 20 and 2 to 8 degrees for up to 30 days in the fridge. So I'm hopeful and optimistic that once we have the public discourse and hopefully receive the FDA authorization, we should be able to reach - our vaccine should be able to reach the people who need it the most. And I trust the government to be able to assure that distribution.

KELLY: How confident are you that this vaccine is safe? And I'm asking because, as you know, a lot of Americans are wary of a COVID vaccine.

ZAKS: We've been very transparent with our data. There's a little bit of flu-like symptoms that you can get, and we've described that in our release. That's anticipated. That's self-limited. The independent NIH-appointed data safety monitoring committee has not seen any significant reason for concern or for pause on this trial. And so, you know, it's early days. But so far, if you look at the safety and reactogenicity profile, if you look at the level of efficacy, we feel very good about it.

KELLY: And those - the flu-like symptoms - that would be similar to what some people get when they get a flu vaccine. Is that right?

ZAKS: That's exactly right. I think in a minority of cases, they tend to be severe. The people report them - 1 in 10 report them as being severe, inhibiting of their activities of daily life. So I want to be clear about that. But that's uncommon, and those are limited and transient, so yeah.

KELLY: Just very quickly, you mentioned that people who got the vaccine and got sick anyway - they didn't get that sick. Just briefly, might you see some benefits there that this - even if it can't stop everybody from getting sick, it might make the disease less serious?

ZAKS: Absolutely, Mary Louise. I think if you look at the data here, the fact that, yes, we had a few that got sick...

KELLY: OK.

ZAKS: ...But a much, much smaller number and no severe disease, I think, is very reassuring for us.

KELLY: OK - Tal Zaks, chief medical officer of Moderna, speaking to us via Skype.

Thank you.

ZAKS: Thank you. Transcript provided by NPR, Copyright NPR.