The first new smallpox vaccine in decades is being tested nationwide, and Missoula is the only site in Montana participating in the study.
Smallpox is a serious contagious disease that was a global scourge until it was declared eradicated in 1980. The last known naturally occurring case in the world was in Somalia in 1977. But threats of bioterrorism have brought smallpox to the foreground. In his 2003 State of the Union address, President Bush called for smallpox vaccinations for a small group of people who would respond in a bioterrorism crisis. He also gave federal support to the development of new vaccines.
"People who know about these things do believe that smallpox is out there and in a form that could be aerosolized and used in an attack," he said. "For a variety of reasons, I think it's a reasonable thing to be prepared for."
The United States has 20 to 30 million doses of vaccine stockpiled, not enough to protect the nation in a widespread attack, Risi said. U.S. manufacture of smallpox vaccine stopped in 1982. The vaccine made before that, called Dryvax and made by the pharmaceutical company Wyeth, has been freeze-dried and stockpiled.
That vaccine was made with old technology, Risi said. It involved inoculating the skin of a calf with vaccinia, a pox virus related to smallpox, and using the calf lymph related to the infection to make the human vaccine.
The new vaccine, being made by the Acambis company, is made using the same strain from the same stock of vaccinia but produced using modern technology, Risi said.
The new vaccine is in its third phase of development. In the first phase, it was checked for unanticipated side effects and toxicities and its doses adjusted. In the second phase, it was tested to see if it worked.
The investigational vaccine is now in trials in 75 sites comparing it to a placebo and to the existing vaccine. A total of 4,800 people will be enrolled in the trial, 2,400 of them 18 to 30 years old and never vaccinated for smallpox, and 2,400 of them 31 and over. The high-profile study will close when it's full, Risi said, and sites on the East Coast have been enrolling subjects for several weeks.
Participants in the study will have screening blood work and a physical exam. They will be examined at intervals of seven, 10, 21 and 30 days and will be interviewed by telephone at three months and six months.
The trial has medical restrictions for participants and is not open to people with certain health conditions, such as HIV infection, or life circumstances, such as pregnancy. It is not open to anyone younger than 18.
The old smallpox vaccine protected against the disease for three to five years, at least; beyond that, its effectiveness is not known.
According to the Centers for Disease Control and Prevention, side effects from the current vaccine included arm tenderness and fever to encephalitis and severe body rash; in rare cases, the vaccine can cause life-threatening and sometimes fatal complications.
The new vaccine is more pure, Risi said, so it may produce fewer side effects, he said.
"There really is no reason to expect it to have more or as many side effects," he said. "There's every reason to think this will be as good and probably safer."
Risi is interested in the trial because he believes vaccines are the wave of the future of disease prevention. It also benefits doctors and patients locally, he said.
"Anybody who's involved in clinical research is a better physician," he said. "But to the community, it brings the cutting edge of defenses to the community for everybody's benefit."
Reporter Ginny Merriam can be reached at 523-5251 or gmerriam@missoulian.com.
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