VACCINES / U.S. Smallpox Threat May Be Exaggerated

The need to vaccinate all Americans against smallpox may be less pressing than people thought, according to researchers from the University of North Carolina at Chapel Hill.

Amid fears that the United States is vulnerable to a bioterrorism attack involving smallpox, tests on people vaccinated more than 35 years ago show that many of them still carry a significant amount of immunity to the disease.

The finding, published in the Aug. 29 New England Journal of Medicine, appears to go against conventional wisdom that smallpox inoculations are only effective for seven to 10 years.

Dr. Jeffrey Frelinger and his colleagues said resistance to the disease among people vaccinated decades ago is waning, but not rapidly. “We would think that people even 35 years later would still have substantial resistance to smallpox infection,” he said.

Smallpox was declared eradicated in 1980, but some experts are pushing to have all citizens vaccinated or revaccinated out of a fear that the virus, which can kill one-third of the people it infects, could be used in a biological attack. Routine vaccinations against smallpox in the United States stopped in the 1970s. Washington has ordered millions of new doses of the vaccine, but is working to “stretch out” existing vaccine supplies by diluting them.