> We know that there are no side effects that are common enough to be of real concern
No, we can't know that. Some affects don't show up for a long time. One example is women.
Women's bodies are complex because they go through so many changes. These changes affect how they respond to medical treatments. In other words:
- Just because pre-menopause women respond well doesn't mean post-menopause women will.
- Just because pre- or post-menopause women respond well doesn't mean women who are going through menopause respond well.
- Just because non-pregnant women respond well to the vaccine for a month doesn't mean that pregnant women will respond well.
- Just because 6-month pregnant women respond well doesn't mean 3-month pregnant women will respond well.
- Any issues with the vaccine during pregnancy may not show up until after the child is born.
- Women's hormones are fluctuating wildly at the beginning and after pregnancy. These are also times that need a lot of representation in the study.
In fact, the amount of change women's bodies undergo affects medical treatment so much that many clinical trials deliberately under-represent women to simplify the study, and then use the results of the trial to recommend prescriptions for women.