Had the cancerous cells built up faster, officials would have seen the symptoms of leukemia and exempted him from getting the vaccine, Lederman said. Or, if he had gotten the vaccine several months earlier, she said, his immune system probably could have cleared the vaccinia without much trouble.
"It's a fluke, really," Lederman said.
More than 1.7 million service members have been vaccinated against smallpox since 2002 because of fears of a bioterrorism attack. Most simply develop a tiny blister that scabs over after 14 days. The scab typically falls off by the 21st day, leaving a barely visible circle of new skin on the arm.
But the military knows it is risking potentially fatal side effects to protect service members, who are exposed to diseases most Americans never encounter.
About 200 service members have developed complications associated with the smallpox vaccination that were serious enough to require hospitalization or absence from work, according to Lt. Col. Patrick Garman of the Military Vaccine Agency. Problems included inflammations of the brain and parts of the heart.
Most of these people recovered, but in one case in 2003, two expert panels concluded that a group of standard deployment vaccines, including the one for smallpox, probably contributed to the death of Army Spc. Rachel Lacy.
In 2007, a vaccinia infection also nearly killed a 2-year-old Indiana boy who contracted the virus from his father, a recently vaccinated serviceman. The boy, who was vulnerable because he had the skin condition eczema, developed vaccinia lesions over 50% of his body. He recovered after he received an experimental drug.
This low rate of serious problems is still high enough to keep public health officials from mandating smallpox jabs for the general population, experts said. After all, the disease has been eradicated as a natural infection since 1980.
But because the military still thinks there is a credible threat of bioterrorism with smallpox, one of the deadliest diseases known to man, officials remain committed to inoculating service members, said Dr. Michael Kilpatrick, who directs strategic communications for the Military Health System.
Military officials said that they were doing their best to reduce complications by asking about preexisting conditions, but that they couldn't catch everything.
"The reality is, we're never going to have zero risk on a vaccine," Kilpatrick said. "There's always going to be that individual that has some untoward event that would occur."
