Because smallpox is a plague of Biblical ferocity that they've only seen in textbooks. Also, normal reactions to vaccination are more traumatic than they're used to seeing.
Here's a good thread...
Smallpox shots sicken some, startling researchers
As physical specimens, the Baylor University students were fit and healthy, the "crème de la crème," in the words of researcher Kathy Edwards. Yet when she inoculated them with smallpox vaccine, arms swelled, temperatures spiked and panic spread.
It was the same at clinics in Iowa, Tennessee and California. Of 200 young adults who received the vaccine in a recent government study, one-third missed at least one day of work or school, 75 had high fevers and several were put on antibiotics because physicians worried that their blisters signaled a serious bacterial infection.
Even for experts such as Edwards, the Vanderbilt University physician overseeing the study, the side effects were startling. "I can read all day about it, but seeing it is quite impressive," she said. "The reactions we saw were really quite remarkable."
President Bush may announce plans, perhaps as early as this week, to resume vaccinating Americans against smallpox as part of a massive push to protect the nation from a biological assault. As he weighs the decision, researchers are becoming reacquainted with the unpleasant — often severe — complications of the vaccine itself.
The experiences in a half-dozen clinical trials offer an early look at what military personnel, hospital workers and other emergency workers will likely encounter if Bush adopts the recommendations of his top health advisers to vaccinate up to 11 million people in the coming months. What is disconcerting, say the people participating in the clinical trials, is that when it comes to smallpox vaccination, what had once been considered ordinary is rather extraordinary by today's standards.
"I just wanted to go to bed for a day or two there," said Alison Francis, a New York University student who received the vaccine. Francis, 24, said she felt tired and achy after getting her shots. Her arm was heavy, warm to the touch and terribly itchy, she said.
Once among the deadliest scourges on Earth, smallpox was declared eradicated worldwide in 1981. But growing hostilities with Iraq and with Osama bin Laden and other terrorists have renewed fears that the virus could be used as a potent, stealthy weapon. Vaccination is surefire protection, but it is risky. For every 1 million people vaccinated, from 15 to 52 will suffer life-threatening consequences such as brain inflammation, and one or two will die, according to historical data. Pregnant women, babies, and people with eczema or weak immune systems should not receive the vaccine.
Federal researchers have been testing the 40-year-old vaccine for its safety and potency. None of the 1,500 volunteers have died or been seriously injured by the vaccine. But even the most mundane cases can be disturbing to doctors and patients unaccustomed to the live virus used in the vaccine and its side effects.
Unlike most modern vaccines, the smallpox vaccine is administered by 15 quick pricks that literally "establish an infection in your skin," said Julie Gerberding, director of the Centers for Disease Control and Prevention in Atlanta. "There is the immediate discomfort of getting poked in the arm and a range of annoying reactions."
Within three to four days, an itchy bump develops, followed by a larger blister filled with pus. In the second week, the blister dries into a scab that usually falls off in the third week. During the three weeks, many people experience flulike symptoms — aches, fever, lethargy — and terrible itchiness.
"You can't scratch it, it's all bandaged up; all I could do was smack it," said Meg Gifford, a University of Maryland junior who participated in one study. She suffered from a slight fever, an arm that was hot to the touch and swollen lymph nodes in her armpit.
"The reactions we are seeing are totally out of line with today's vaccine experience and absolutely in line with historical experience," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "In the 30 years since we had routine vaccination, the public's tolerance level has gone way down."
Maryland researchers have begun a second trial revaccinating older adults to see how much immunity stays in the system. Early indications are that people who have been previously inoculated do not suffer as many severe side effects.
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