Pfizer (PFE -5.12%) and BioNTech (BNTX -1.01%) recently disclosed six-month efficacy for their COVID-19 vaccine. In this video from Motley Fool Live, recorded on April 5, Fool.com Contributors Brian Orelli and Keith Speights discuss why investors and patients shouldn't be worried about a slight drop in efficacy. They also discuss the likelihood of getting severe disease -- it's low no matter whose definition you use -- and also talk about the vaccine's ability to protect against the South African variant.
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Brian Orelli: Our first story is about Pfizer and BioNTech. They reported updated data on their phase 3 clinical trial. The efficacy went down from 95% when it was first reported to a 91.3% when looking up to six months after the second dose. They had 100% efficacy in preventing severe disease, if you define it by the CDC's definition of severe disease, and it was 95.3% if you use the FDA's definition of severe disease. Then there was 100% efficacy at preventing the South African variant, although that was only six cases. Six versus zero, so I don't think we can quite call it 100% yet. Should we be worried about the dip in efficacy and any other thoughts on the data?
Keith Speights: No, there is no reason at all to worry about the lower overall efficacy. Like you said, Brian, Pfizer and BioNTech, in these updated results, they were measuring up to six months after the second dose. That initial efficacy result of 95% was much closer to the administration of the second dose of the vaccine. So you would expect maybe a little bit of degradation there, and that's what we're seeing. Nothing big, just a few percentage points, so no reason at all to worry.
Look, this vaccine remains highly effective from everything we can tell. In my view anyway, the most important numbers are still the efficacy in preventing severe disease of COVID-19. Those numbers remain really good, whichever definition you use, whether it's the FDA definition which gives it a 95.3% efficacy or the CDC's definition of severe disease, it gives it 100% efficacy. Look, those are great numbers either way.
That 100% efficacy against the South African variant rather is encouraging. But like you said, there's some really low numbers involved in this study. I think there were only 800 participants in the South African study that Pfizer and BioNTech conducted, that's not an awfully large number of participants in a clinical study and only nine cases of COVID in total were observed in that study in South Africa, six of those were the South African variant and all of those cases occurred in the placebo group. It's very encouraging to see that kind of result against this South African variant. Still early, but I think Pfizer and BioNTech walked away from this latest update feeling pretty good about the vaccine.
Orelli: I'd definitely like to see more data on the variants, but besides that, we're missing data, which they just can't give us, at least not yet. I think the rest of the data looked really positive.
Speights: Right, I agree.