Researchers have developed a smallpox vaccine from plants that they say is both highly effective and safe. VOA's Jessica Berman reports from Washington.

Smallpox has been virtually wiped off the face of the earth using a highly effective vaccine made from the live weakened virus that causes the disease. Unfortunately, in some people, the drug causes serious side-effects.

Routine smallpox vaccination among the American public stopped in 1972 after the disease was eradicated in the United States. But the U.S. military resumed smallpox vaccinations in 2002 because of bioterrorism fears.

Now, researchers have developed a smallpox vaccine that they say is completely safe using a non-infectious viral protein and tobacco and collard plants. Such an approach is called recombinant technology.

In experiments with mice, the vaccine was 100 percent effective in protecting the animals against smallpox.

Results of the study are published in the journal Proceedings of the National Academy of Sciences.

Hilary Koprowski of Thomas Jefferson University is the study's lead author. "I consider as far as our research work, [the study] is finished," he said.

Before any drug could be put into general use, there must be clinical trials to determine whether it is safe and effective.

Samuel Bozzette is a senior scientist at the Rand Corporation, which studies public policy questions. Rand has recommended using the old vaccine to inoculate medical personnel who need to deal with people infected with smallpox in the event of an attack.

Bozzette says a safer vaccine may now make it possible to carry out such a plan.

"The availability of a safe, recombinant vaccine would be a big step forward in implementing what people believe would be a prudent policy of vaccinating a certain portion of the population right now," said Samuel Bozzette.