Not everybody can safely be vaccinated against smallpox using the current FDA-approved vaccine. Scientists hope another study vaccine, now undergoing its first testing in the United States at Saint Louis University, will give a choice to people who can't be given the current vaccine, known as Dryvax.

There are limits to the current vaccine," said Sharon Frey, M.D., from Saint Louis University's Center for Vaccine Development. "You can't give Dryvax to people with certain skin conditions, such as eczema, or to people who are immunosuppressed. So, for example, if you are HIV-positive or undergoing chemotherapy for cancer, you shouldn't receive the currently licensed vaccine."

Dr. Frey said this study vaccine, known as MVA-BN and provided through Bavarian Nordic, is different than other vaccines that are now available. Like the current vaccines, the study vaccine is a live-virus vaccine made from vaccinia virus, but this study vaccine contains a much more "attenuated," or weakened, form of the virus.

"The thinking is that the study vaccine is much more attenuated, therefore the side effects should be less. So the hope is you may be able to give it to someone who is immunosuppressed. These are some of the questions we'll be studying as we start testing this investigational drug. If our studies prove successful, we hope this vaccine can be given to people for whom Dryvax is contraindicated."

MVA-BN also is administered in a different way. Dryvax is administered using a method called scarification, in which the skin is poked with a bifurcated needle just enough to puncture the skin. The study vaccine being tested will be administered intramuscularly, as a flu shot is given, or subcutaneously between the skin and muscle, as an insulin shot is given.

The study will enroll 90 adult volunteers into six different groups. MVA-BN will be given in three different dose strengths alone or in combination with Dryvax. The study is sponsored by the National Institute of Allergy and Infectious Diseases.

Volunteers must be between 18 and 32 years of age, generally in good health with no chronic illness, no heart disease, no history of serious allergic reaction, no immune system problems and no eczema or other significant skin conditions. Potential volunteers who have significant contact with anyone who is pregnant or with a child less than 12 months of age will be excluded. Volunteers must NOT previously have been vaccinated against smallpox.