First AZ announces a 79% effective vaccine when it was only 76% (https://www.npr.org/2021/03/24/981042289/latest-astrazeneca-report-supports-effectiveness-of-covid-vaccine#:~:text=The%20latest%20analysis%20finds%20the,or%20critical%20disease%20and%20hospitalization). This was because AZ left out some more recent data in their announcement. The net-net was both a 'who cares' and wonderment why the company would have been deceptive when the results were very good, and almost the same anyway.
Today, Pfizer just made a similarly deceptive announcement (see CNN article here, but just to make sure it wasn't CNN's error, I checked Pfizer's website, which said "in participants aged 12-15 years old, BNT162b2 demonstrated 100% efficacy, exceeding those reported in trial of vaccinated 16-25 year old participants in an earlier analysis...")
What is this 100% efficacy based on? A small study where 18 people in the control group got COVID vs. 0 in the treated group. While that is technically 100% effective, there is no indication it is different than the 95% effectiveness seen for other age groups, and it is wrong to say it is different. With 95% effectiveness, there would be just 1 infection in the group that got the vaccine for every 20 in the group that did not. Here, we're only at 18--even without much statistical analysis, one can imagine that you would need more data to conclude that it is better than 95%. Given the data they have collected so far, one can reasonably conclude that the effectiveness is somewhere between 81% and 100%, with 95% confidence. In short, there is absolutely no reason to believe Pfizer's statement of 100% effectiveness. Of course, even 81% would be great and clearly the vaccine, if proven safe for younger people, will be approved at this effectiveness, but it's unfortunate that Pfizer chose the same deceptive practice that AZ did.
Note that for nearly every vaccine, we have heard that they are 100% effective at preventing severe disease. Once again, they are being deceptive. In almost every case, there were too few people with severe disease in the control group to conclude the chances of severe disease were reduced further than the vaccine reduced the chances of disease in general.
Let's take Astra Zeneca, who headlined their press release with "COVID-19 Vaccine AstraZeneca confirms 100% protection against severe disease, hospitalisation and death"). What does the real data say? For the AZ vaccine, the article AZ cites says there were 15 hospitalizations (apparently 0 deaths) in the control group vs 0 in the treated group. This implies that the drug is somewhere between 78 and 100% effective against hospitalization. This is great, but it's not 100%, and it's not even clear that it is much more effective at preventing severe disease as it is against preventing COVID. There's just not enough data in yet.
These pharma deceptions are puzzling and, when pointed out (as AZ's first claim of 79% effectiveness was), they serve to undermine confidence in the vaccines. This is frustrating, because the vaccines are very very good, and the data do not need to be over-stated to make that claim!