FDA screens out studies with selection bias

The Free Press:

• ..one of the studies looked at a group of people for six weeks—three weeks after they were vaccinated, and then another three weeks after that. If they were healthy after the second three-week period, the researchers concluded that it meant the vaccine was safe. In addition to the absurdly short length of time—six weeks to conclude the vaccine is safe?—it has an obvious and inherent bias toward healthy people, who are the most likely to get vaccinated. 

•  Another study used an approach called “test negative”: It looked at people who came to the hospital with flu-like symptoms, some of whom had Covid and some of whom didn’t. If the group who were vaccinated had fewer people with Covid, it was supposed to mean that the vaccine worked. But in reality, it could simply mean that people who are vaccinated are more likely to show up at the hospital.