Disclaimer: layman here, just repeating what I heard and read the past months/years. > How much care is given to ensure the jab group's demographics reflect th

Disclaimer: layman here, just repeating what I heard and read the past months/years. > How much care is given to ensure the jab group's demographics reflect the "control" (i.e., the broader population). This is mostly done through sampling all ages. In general, older people have a weaker immune system than younger, so older people can serve as a model for younger, immune-suppressed people. That's not ideal, but generally preferable to testing new drugs in chemo patients. In cases where people have an elevated risk (chemo, pregnancy, other immune suppression situations like after transplants), the best you can do is vaccinate as many of the contact persons around them. (Regarding pregnancies, I don't know how much of that is actual risk regarding vaccination, and how much is related to the difficulty of testing drugs on pregnant women. For example in Germany, drug tests are on pregnant women are a very delicate topic and mostly avoided by pharma companies, mostly due to https://en.wikipedia.org/wiki/Thalidomide_scandal https://en.wikipedia.org/wiki/Thalidomide_scandal )