AstraZeneca (NASDAQ:AZN) hopes to soon win approvals around the world for its COVID-19 vaccine candidate AZD1222. However, the British drugmaker's recently announced interim efficacy results from a late-stage study raised eyebrows. In this Motley Fool Live video recorded on Dec. 3, 2020, Healthcare and Cannabis Bureau Chief Corinne Cardina and Fool.com writer Keith Speights discuss what's behind AstraZeneca's COVID vaccine controversy.

Corinne Cardina: Let's turn now to catch-up with AstraZeneca and the University of Oxford's vaccine candidate. We talked about this on previous segments, but there's been a lot of noise in the media, confusion surrounding the data that they first released. Why are there questions about this data's reliability? What are the next steps for AstraZeneca and Oxford University before they can really be in that position to get a green light?

Keith Speights: AstraZeneca really didn't provide as much transparency as many observers would have liked with their announcement of their interim results for their vaccine, AZD1222. First of all, Corinne, they came out and said that they had an average efficacy of 70 percent. But they said, "But there is a group that has a 90 percent efficacy."

Well, first of all, there's really not such a thing as an average efficacy. The vaccine either has an efficacy of a level or it doesn't. What they did, was they merged data for a larger group of participants that only had an efficacy of 62 percent, which isn't all that great, especially in comparison to Pfizer's and Moderna's results, and they merged that data with smaller group that had the 90 percent efficacy and came out with that 70 percent average.

I think a lot of people looked at that and said, "AstraZeneca, what are you trying to pull here? You can't just do that." There were even some questions about that smaller group. It ended up being, I think one of AstraZeneca's executives said it was "serendipity" that they provided a half dose, followed by a full dose that achieved that higher efficacy.

Well, serendipity is one way of putting it. Another is it is just a mistake. It was pure luck. What happened was that some of their, I think a contractor was already going with a half dose, regimen first, and then a full dose, AstraZeneca found out about it and said, ''Oh OK, let's just go with the flow'', and it turned out that was the group that had the best efficacy.

There are really some questions about their trial protocols in different countries, in different subgroups, and I think AstraZeneca basically stirred up a hornet's nest with how they unveiled their data.

Corinne Cardina: Keith, I don't like serendipity with my science. Those are two things I want to keep very separate. We will be keeping a close eye on a future study that they are going to do to try to get a little bit more information.

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