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WHO Warns Against Mass Smallpox Vaccination

The World Health Organization is warning against a mass smallpox vaccination campaign in the wake of fears the disease could be used as a biological weapon. But the health agency says any sign of a smallpox outbreak would be viewed as an international emergency.

Although the World Health Organization helped to eradicate a natural occurrence of smallpox world wide 20 years ago, bioterrorism experts say it is a disease that could be used as a biological weapon.

The United Nations health agency says any country that feels it could be threatened by the deliberate use of the virus has the right to consider stocking vaccine. But the WHO director of communicable diseases, David Heymann, warns against the vaccination of entire populations. "The vaccine is not 100 percent safe," he says. "For each one million people vaccinated, we know that one will die from a side effect. We know, in addition, that there will be some neurological damage in many, many more."

Dr. Heymann says the vaccine can even work if it is administered soon after exposure, because smallpox has an incubation period of 7 to 14 days. "If you vaccinate someone who has been exposed during the first three days after exposure, there is enough time for the human body to develop immunity," he says. "And, there will either be no infection, or if there is infection, there will be a very mild case of smallpox."

Unlike anthrax, smallpox is highly contagious and was fatal in about 30 percent of cases. It spreads through saliva droplets in a person's breath. There are fears that smallpox could spread more rapidly even than it did in the past, with greater international air travel.

WHO says the way to contain the disease would be to identify and isolate people who have the virus, and vaccinate them.

The health agency says its experts made an official review during the past six weeks of the only known stocks of the live virus, which are contained in two laboratories, one in the United States and one in Russia.