Possible designs for the Salk polio vaccine trial described in Box 4.2 might include giving the vaccine to second-grade children in one region and comparing the rate of polio in this group to the rate...

Possible designs for the Salk polio vaccine trial described in Box 4.2 might include giving the vaccine to second-grade children in one region and comparing the rate of polio in this group to the rate in: – Second-grade children in another region where the vaccine was not used – Second-grade children the year before the vaccine was introduced – First- and third-grade children in the same region and year as the vaccinated group. What are the strengths and limitations of each of these designs and which do you think would be preferable and why?

Box 4.2