Scientists launch smallpox vaccine study

ST. LOUIS -- St. Louis University researchers have launched a new smallpox vaccine study, hoping to pinpoint whether diluted vaccine can boost the presumed waning immunity of those inoculated more than three decades ago.

While conventional wisdom holds that vaccination against smallpox will provide significant protection against the disease for at least a decade, it's unclear how long immunity to smallpox lasts, a researcher said Monday in announcing the latest study.

"We're undertaking this study because of increasing concerns about the use of biological agents in warfare and terrorism around the world," said Dr. Sharon Frey, the study's chief investigator and a St. Louis University associate professor of infectious diseases and immunology.

Two previous studies at the school, including one since the Sept. 11 terrorist attacks, involved adults younger than 32 who had never been vaccinated against smallpox.

Researchers hope to recruit 90 volunteers who were vaccinated against smallpox as children for the latest study.

The researchers will assess the effectiveness of diluted versions of Dryvax, a smallpox vaccine no longer produced and in limited U.S. supply. Researchers will divide participants into two groups -- people 32 to 60 who were vaccinated as children, and people 18 to 32 who were never vaccinated.

Frey said the study's 80 previously vaccinated volunteers will get undiluted vaccine or vaccine diluted by 3.2, 10 or 32 times.

The 10 participants never vaccinated will get undiluted vaccine.

Volunteers should be healthy adults without eczema or immune-system problems, and they should have no contact with anyone who is pregnant, has eczema or immune-system deficiencies.