They don't just select from the population at random from these studies. For example the study excludes those over the age of 85 or those that are immunocomporm

They don't just select from the population at random from these studies. For example the study excludes those over the age of 85 or those that are immunocompormised. You can see more details on the exclusion criteria listed in seciton 5.2 of the Pfizer study: https://pfe-pfizercom-d8-prod.s3.amazonaws.com/2020-09/C4591001_Clinical_Protocol.pdf https://pfe-pfizercom-d8-prod.s3.amazonaws.com/2020-09/C4591...