US President George W. Bush is to make the smallpox vaccine available to all Americans on a voluntary basis to guard against a bioterrorist attack.
As a first step, he will order military staff to begin getting smallpox vaccinations and will start a plan to offer the vaccine to emergency medical workers and response teams within weeks.
The public will be offered the vaccine on a voluntary basis as soon as large stockpiles are licensed, probably early in 2004.
Smallpox was declared eradicated from the world in 1980, but experts fear that it could be used by hostile nations or terrorist groups in an attack. Intelligence experts believe that four nations, including Iraq, have unauthorised stocks of the virus.
Routine smallpox vaccinations ended in the United States in 1972, meaning nearly half the population is without any protection from the virus. Health officials are not sure whether those vaccinated decades ago are still protected from the disease.
The vaccine has risks of its own. Based on studies from the 1960s, experts estimate that 15 out of every million people vaccinated for the first time will face life-threatening complications, and one or two will die. Reactions are less common for those being revaccinated.
Using these data, vaccinating the nation could lead to nearly 3,000 life-threatening complications and at least 170 deaths.