I'm no expert so I'm only going by what "experts" say. I read early on that Sinovac was the only one that was being peer reviewed. It was from the US media. Sanjay Gupta of CNN who doesn't seem to be political in his reporting was the most recent person maybe less than a month ago who said to viewers like he was reminding people that the data coming out is still from the companies producing these vaccines so there's room for skepticism if the data is accurate. Dr. Fauci and Dr. Birx were early seen as being trustworthy but then you can see later political pressure being applied where they had to find a middle of road answer for questions they were being asked. Like I said, I'm no expert but I can see pressure and influence being applied to say certain things meaning there's some measure of manipulation of the facts going on.
I believe Dr. Gupta was referring to the difference between clinical trials (typically conducted by the companies themselves) and real-world data collected by countries currently administering the vaccines to the general public. And he's more specifically referring to the real-world data coming out of Israel.
I don't think he's saying that the clinical trial data given by the companies themselves are less trustworthy. Not at all. He's simply pointing out a shortcoming of any clinical trials. In any clinical trials, no matter how careful you choose your subjects, you will have some kind of bias simply because you are limited by the size of your pool. Although the COVID vaccine trials conducted by Pfizer and Moderna each contained about 30,000 - 40,000 people, this is nothing compared with millions/billions of people in the real world. You inherently introduce some kind of bias. This is expected of any kind of clinical trials. This is why the Israeli data are so important and so exciting.
With that being said, we cannot deny the significance and legitimacy of these clinical trials. Especially when they have been scrutinized by peers and officially published, they carry so much weight. They provide invaluable information.
