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Is COVID Vaccine Efficacy Really Falling?

By Keith Speights and Brian Orelli, PhD – Sep 12, 2021 at 5:57AM

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Some experts are skeptical.

More fully vaccinated individuals are being infected by the coronavirus. It seems to make sense that the efficacy of COVID-19 vaccines is declining. However, some healthcare experts aren't so sure that's actually true. In this Motley Fool Live video recorded on Sept. 1, 2021, Motley Fool contributors Keith Speights and Brian Orelli discuss whether or not vaccine efficacy is really falling.

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Keith Speights: While the U.S. is at least tentatively gearing up for booster doses. There's actually some skepticism that COVID-19 vaccine efficacy is actually waning. Now that view does seem to differ from what we're seeing with increased breakthrough cases among fully vaccinated individuals. But why are some experts going against the conventional wisdom here?

Brian Orelli: I'm not sure if there is a conventional wisdom, [laughs] but there's certainly wisdom and counter wisdom. I think the problem here is that you don't have a control group that got placebo.

You can compare people who got the vaccine earlier with the people who got the vaccine late, and that's what the study in Israel did. But to make a firm conclusion, you have to assume those groups are actually similar. If they're not, because maybe the group that got the vaccine earlier is richer and so therefore more likely to travel and more likely to go out to eat and so therefore more likely to be exposed to the virus. Then they might just be getting the breakthrough cases at a higher rate because they are more exposed to the virus, which has nothing to do with vaccine protection waning.

You can also look at the rate of infection for the people who got the vaccine over time. But that assumes again the same exposure to the virus over time. If they are going out more because they feel more confident about other people being vaccinated and so they're protecting themselves the least wearing less masks than you would expect them to get more breakthrough cases. Just because they are exposing themselves and more to the virus, not because they're antibodies are going down and that the vaccine is no longer able to protect them.

The increase in breakthrough cases is due to higher exposure than arguably, we'd be better off given the vaccines a way to help stop the spread globally, which would help protect us from a creation of stronger variants. There's definitely an argument for, if the issue is that we're just exposing ourselves more to the virus and that's the reason why we're getting more breakthrough cases, then that's a completely different case than the antibody levels are going down enough that we can now get COVID-19.

You can look at antibody levels and it's either they're going down but you don't know where the level is that would result in you not being protected, and so that's the question at this point, I think.

Speights: Pfizer (PFE -0.12%) has been saying, the antibody levels are going down. Therefore, we think booster doses could be necessary. But as you mentioned Brian, that there is no control group here and there are multiple factors at play, so there's no way to be 100 percent certain.

I think that's back to what we were talking about earlier in this segment. The issue here is that there's just not a lot of data to go on.

Orelli: Antibody levels are not even all that we need. We also need to know you're protected by antibodies levels as your first line of defense, but eventually, your immune system has memory B and memory T cells that they recognize the virus and then ramp back up on production of antibodies and T cells that can kill the cells that are infected with the virus.

There's those even harder to measure. So just measuring antibody levels doesn't even really tell you whether you're actually protected against the virus.

Keith Speights owns shares of Pfizer. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.

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