Exactly. For the most part, the comments you make are accurate. The issue is what specifically puts individual patients at risk of a serious reaction. If there are genetic variants in certain individuals that put them at risk, they could be responsible for many of the reactions that currently occur with biologics and drugs.
In the example I provided the last time about codeine, there was a duplication of a specific gene responsible for converting codeine into its active form in the body--morphine--and another genetic variation. Instead of converting morphine into an inactive form that was excreted by the body, it converted it into another active form of morphine that increased its effect on the brain, and therefore its effect on bodily function. That is what killed a child in Ontario, as we reported in The Lancet medical journal, I believe in 2006.
So human genetics is definitely at play here in terms of response, and how we uncover those genetic differences is important in all of this post-market debate. One of the concerns I have is that just collecting reports on individuals who experience reactions isn't enough; we need a control group. One of the things that research is quite clear about is the need to look at another group of people that don't experience a reaction and understand what makes them different from the people who do experience them.