What does 95% efficacy mean?
EliotH 28 Apr 2021
It is well known that pharmaceutical companies play statistical games. For example they tout 33% risk reduction for statins that sounds like 33 out of 100 people will be saved from a heart attack, when the real data shows that the Number Needed to Treat (NNTT) is more like 88 people for 5 years to prevent 1 cardiac event. They do the same thing with flu vaccines. Sixty percent efficacy doesn't really mean 60 out of 100 people are protected from getting the flu.
So this guy says the NNTV (V=Vaccinate) for Moderna is 176 to 1306.
https://www.bmj.com/.../bmj.m4471/rr-0
(I don't know how much C&P is allowed here. It's a Rapid Response in BMJ and just two paragraphs.)
joelcairo 28 Apr 2021
It's the "retired pediatrician" who is playing the statistical games in that article. He's watering down the data with all the people who DIDN'T get sick during those few months of a short-term clinical trial.
The fact is, without vaccines pretty much EVERYONE is going to contract COVID-19 sooner or later, so a highly effective vaccine is a godsend. I recommend getting your vaccine advice from the CDC or equivalent, not random retired pediatricians.
joelcairo 29 Apr 2021
EliotH 30 Apr 2021
Here is an article I found in The Lancet.
https://www.thelance...0069-0/fulltext
ARR is also used to derive an estimate of vaccine effectiveness, which is the number needed to vaccinate (NNV) to prevent one more case of COVID-19 as 1/ARR. NNVs bring a different perspective: 76 for the Moderna–NIH, 78 for the AstraZeneca–Oxford, 80 for the Gamaleya, 84 for the J&J, and 117 for the Pfizer–BioNTech vaccines. The explanation lies in the combination of vaccine efficacy and different background risks of COVID-19 across studies: 0·9% for the Pfizer–BioNTech, 1% for the Gamaleya, 1·4% for the Moderna–NIH, 1·8% for the J&J, and 1·9% for the AstraZeneca–Oxford vaccines.
joelcairo 30 Apr 2021
The point is they're not testing to evaluate how many cases in the population they can reduce. They're only interested in measuring cases in the placebo group vs. cases in the vaccine group, which is why they stopped as soon as they hit 95 cases.
It makes little difference whether there were 90 people in the placebo group and they all got sick, or there were a million people in the group and hardly any of them got sick. The vaccine was enormously effective at reducing diagnosed cases. That means if nearly everyone in a country were vaccinated, the number of cases would quickly fall to almost zero.