I am also Senior Vice President for Epidemiology at Ingenix Pharmaceutical Services. I hold doctoral degrees in medicine and public health. I have published widely, and I serve on scientific, advisory, and editorial boards. I have been a consultant to the World Health Organization, national governments, and most large manufacturers of drugs and vaccines. I want to talk about the value of doing population-level thinking when we talk about vaccine safety and efficacy.
Clinical scientists establish cause and effect by looking at groups of people.
Imagine that we vaccinate 100 people who are facing a smallpox epidemic that would be expected to kill a third of them. Suppose that all of them live. We suspect that the vaccine caused the good outcome. Whenever we give the vaccine, all live, and whenever we fail to give it, many die. We can say that the vaccine prevents death.