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Title

Clarifying efficacy percentage (vs. effectiveness)

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In a recent article <a href="{app}/view_article.php?id=4385">Links and Notes for December 17th, 2021</a>, I noted that Doctor Mark Hanefeld seems to be underselling vaccine efficacy (predicted) and effectiveness (measured). The podcast is linked below, <media href="https://www.youtube.com/watch?v=oSJ-mGcFalY" src="https://www.youtube.com/v/oSJ-mGcFalY" source="YouTube" width="560px" author="NDR Ratgeber" caption="Coronavirus-Update Sonderfolge: Gerüchte und Fake-News zur Impfung einordnen | NDR Podcast"> At <b>17:30</b>, Herr Doktor Marc Hanefeld says, <bq>Nehmen wir mal einfach die Zulassungsstudien zu Biontech. Da haben wir eine 95% Effektivität. Und die Effektivität ist immer im Hinblick auf symptomatische Ansteckung. Das heisst, man wird angesteckt mit dem Virus und merkt was---hat Symptome. Diese hat 95% Effektivität am Anfang. Das heisst 5%---sprich jeder zwanzigste---konnte sich trotzdem anstecken. Würde nicht schwer krank werden aber kann das Virus weiter geben.</bq> A lot of what he had to say was very, very good. But my ears perked up at this explanation, because it's wrong---it drastically undersells the efficacy of the vaccines (or any vaccine).<fn> The 95% protection is <i>relative to people without the vaccine</i>. It means that of the number of unvaccinated people who became ill with COVID (in the control group), only 5% as many vaccinated people got it. The 5% is not applied to the entire vaccinated group, but to the percentage of unvaccinated people in the control group who became ill. If each group had 10,000 people and about 100 people in the control group became ill, that means that only 5 vaccinated people <i>of the 1000</i> because ill. That means that, while you had a 1% of getting sick without the vaccine, you had a .05% chance of getting sick if vaccinated. It was never perfect, but it was incredibly good. Hanefeld's formulation makes it sound like you have a 5% chance of getting infected when it's actually much better than that---even with the waning effectivity of the vaccines against new variants and over time, the protection number you hear is still calculated in the same way---as a percentage of the likelihood that you'll be infected without it. So a 50% protection means that you still only have a 0.5% chance of catching it if an unvaccinated person has a 1% of doing so. On another topic, I was extremely hesitant to say that Hanefeld had formulated efficacy incorrectly (or sub-optimally) because I don't want to be the kind of person who, without any formal training but a lot of "reading" starts disagreeing with experts, thinking that I can run with the big dogs. That's why I found the Lancet reference in the footnotes, to corroborate my gut reaction. The problem we have today is that there are far more people who think that they're smarter than everyone else---with the corollary being that experts are kind of dumb, blinkered by their experience, set in their ways, and/or bought off by corporate interests. They think that they are the only ideologically pure and incisively clever person on the planet, doing humanity a favor by jumping in everywhere and fixing things. This is an attractive plot for a movie, but it's not how reality usually works. Sure, you're going to get so-called experts who <i>are</i> bought off, who <i>are</i> hamstrung by pet theories, but those are generally also the experts who are considered to be damaged goods by other experts. The winnowing process of science and rationality generally works pretty well, if you can control for ego and corporate interest. One way to control for those things is to make sure that the incentives are lined up to guarantee correctness rather than fame. If the incentives allow for people to get famous or rich while pushing something they know is incorrect, then you are doomed to fail. I wrapped that up one day and read, just the next morning, in <a href="https://www.wsws.org/en/articles/2021/12/28/tuiz-d28.html" author="Patrick Martin" source="WSWS">CDC surrenders US population to the spread of Omicron</a>, <bq>Even those fully boosted have only 75 percent protection against Omicron. That means that if 60 million people who have received booster shots come into contact with a COVID-19 case and are sent back to work without even a day off, 15 million of them would be carrying the infection with them to spread.</bq> That sounds wrong, in the same way that Herr Doktor Martin's formulation sounded wrong. And the WSWS would ordinarily be doing everything they can to <i>emphasize</i> the effectiveness of vaccines. <hr> <ft>The article <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00075-X/fulltext" author="Piero Olliar" source="The Lancet">What does 95% COVID-19 vaccine efficacy really mean?</a> agrees, <bq>[...] a 95% vaccine efficacy means that instead of 1000 COVID-19 cases in a population of 100 000 without vaccine (from the placebo arm of the abovementioned trials, approximately 1% would be ill with COVID-19 and 99% would not) we would expect 50 cases (99.95% of the population is disease-free, at least for 3 months).</bq></ft> <ft>I feel like I've been hearing about sanctions on Russia for much longer than the last six years, but I couldn't find any strong evidence of it in a quick search.</ft>