Mayo Clinic Begins Enrolling for Smallpox Vaccination Trial

ROCHESTER, Minn. — Healthy adults ages 18 to 29 are needed for a research study comparing the safety and effectiveness of two different vaccines for the prevention of the smallpox disease.

The study will compare three dose levels of a new vaccine with the current, approved smallpox vaccine that was provided to all U.S. residents during the period of routine smallpox vaccination. The effectiveness of these trial vaccinations will be measured by observing whether or not there is a skin reaction, such as a blister, at the sight of the vaccination. A skin reaction is a typical response to smallpox vaccination. The response also will be measured by examining the size of the skin reaction and the time it takes for the blister to heal. Participants may become immune to smallpox, which would reduce or prevent infection with smallpox.

Smallpox was one of the major causes of death and sickness through the first half of the 20th century, but a global program of smallpox vaccinations resulted in eliminating the smallpox disease. The last cases of smallpox in the United States occurred in 1949 in Texas.

Because of the absence of smallpox, routine vaccination in the United States ceased in the early 1970s. However, the United States government has determined it is necessary to keep smallpox vaccine available, in case the disease returns naturally or because of bioterrorism.