The University of Iowa is one of just four medical research centers chosen to conduct tests of the smallpox vaccine. Dr. Jack Stapleton, a professor in the infectious disease division of the University’s department of internal medicine, will lead the Iowa City study.Stapleton says they’ll be testing whether vaccine the Defense Department bought 40 years ago still works on humans, and whether it can be diluted and remain effective.Stapleton says if the dilution works, then the stockpiles of smallpox vaccine would be enough to give everyone in the U-S and in western Europe a dose.Stapleton says smallpox is a deadly disease that’ll kill about a third of the people infected who aren’t immunized. Smallpox vaccinations ended in the early ’70s in the United States. Some fear smallpox could easily be introduced in the U-S by terrorists, but smallpox vaccinations have been controversial.Once someone gets smallpox, the vaccine can even alleviate symptoms or prevent the person from getting sick. Ninety-five people between the ages of 18 and 32 will be included in the University of Iowa study.