The rational decision-making portion of a risk-benefit analysis for vaccines is fairly straightforward. For simplicity’s sake, you can break down each vaccine into two choices: to give or not to give the vaccine. In reality there are other options such as giving the vaccine on a different schedule or breaking combination vaccines into separate components. If you wanted to include those possibilities, you could represent those options as additional choices in your analysis. For simplicity’s sake, we will just consider the “to give or not to give” options in this discussion.
You then need to ask about the risks and benefits of each decision. For example, if you give the vaccine, you have the risk of side effects. You then need to know how often each side effect occurs and how mild or serious the complications of these side effects are. You will probably have less concern for a two day fever than for a hospitalization for encephalitis. You also need to know how effective the vaccine is so you can calculate the amount of protection or other benefits you might derive from it.
On the other hand, if you don’t give the vaccine, you have the risk of the disease itself. You need to know how common the disease is and how likely you or your child is to be exposed. You also need to know the consequences of the disease, both mild and severe, and how likely those consequences are. Are we talking about a one in a thousand risk or a one in a million?
In the end, you hopefully will be able to judge the relative risk of the vaccine compared to the risk of the disease from your perspective. We have spent most of parts II, III, and IV providing these factual details for the most common vaccines available in the United States.