Study: Vaccine More Long-Lived

Previously thought to last only seven to 10 years, the findings indicate that the vaccine provides significant immunity for as long as 35 years after a person was immunized.

The study, which was published Thursday in the New England Journal of Medicine, puts in perspective the United States' vulnerability for chemical attack.

Jeffrey Frelinger, chairman of the Department of Microbiology and Immunology in the School of Medicine, who conducted the study along with postdoctoral researcher Lawal Garba, said it was a largely unexplored question.

While doing research on a separate HIV study, Frelinger and Garba tested blood samples from 13 laboratory workers who had been vaccinated according to federal guidelines because they work with the vaccinia virus.

The smallpox vaccine contains the live vaccinia virus, not smallpox, or variola virus, but causes an immune response in the body to numerous diseases, including monkeypox and cowpox.

Four of the workers tested for the study were vaccinated less than five years ago, and the rest had been vaccinated either from five to more than 35 years ago.

Putting blood samples in test tubes, the researchers tested the strength of participants' immune systems by recording white blood cells called cytotoxic T lymphocytes, or CTLs, reaction to the vaccine.

Smallpox was thought to be extinct more than 20 years ago, except for minimal supplies kept by the United States and Russian governments for research.

But in the wake of the Sept. 11 and the anthrax scare, public health officials have warned that the disease could be used as a bioterrorism weapon. The disease is easily passed from person to person and kills about one-third of infected people.

Vaccines were commonly given to babies in the United States until 1972, but the program was ended due to the high cost and potential side effects.

Experts estimate that if everyone in the United States was vaccinated, between 300 to 600 people would die and many more would experience fever, muscle soreness and brain swelling.

In June, a federal advisory committee on immunizations unanimously rejected smallpox vaccines for the general public and recommended instead limited immunization of doctors and emergency workers.

Curtis Allen, spokesman for the Centers for Disease Control and Prevention, said the plan, which still has to be approved by Tommy Thompson, U.S. health and human services secretary, calls for the vaccination of about 10,000 to 20,000 people. The program could begin this fall.

Frelinger said more research needs to be done before the policy against widespread immunization could change.

But he said research like his is a step in the right direction.

"I think what our study did was inform about the criteria to immunize," he said. "But the specifics still need to be worked out."

Greg Roa, a spokesman at the National Institutes of Health, said multiple studies are taking place to more extensively explore the issue.

"Everyone here has read the study," Roa said. "It has certainly raised a lot of eyebrows."

The University Editor can be reached at udesk@unc.edu.