Physicians who have administered the smallpox vaccine to hundreds of volunteers over the past several months are reporting side effects of pain, swelling and flu-like symptoms in users. Over 1,500 volunteers have participated in a nationwide study since September 11, 2001 to test the controversial vaccine's safety. According to reports, many users, especially young, healthy volunteers, have developed a sore on the arm where the vaccine is injected and have experienced swelling, pain and redness in the area. More than 10 percent have experienced flu-like symptoms, including high fevers. President Bush is still considering a plan to inoculate 500,000 soldiers and 500,000 healthcare workers with the vaccine.

Although routine vaccinations ended in the United States in 1972 and the disease was declared eradicated from the earth in 1980, the U.S. government fears terrorist organizations or hostile countries such as Iraq may have stockpiled samples of the smallpox virus. Because the smallpox vaccine is so dangerous (it is made with a live virus, vaccinia, that can cause serious injury to those who come in close contact), health officials have determined that one or two people will die for every million vaccinated if the nation is required to administer it.