WASHINGTON – Edward Dudley was vaccinated for smallpox 33 years ago, when he was about a year old, but last week he rolled up his sleeve and volunteered to receive the smallpox vaccine for the second time.
There is an outside chance that vaccine he received Tuesday could give Dudley symptoms ranging from mild flu to serious illness. But it will also provide valuable research for scientists looking for ways to protect the country in the event that smallpox is used in a bioterror attack.
“I’m a cyclist and I bike through downtown Baltimore every day,” Dudley said of the small risk involved in the vaccine trials. “I have much more of a chance being injured doing that than developing an adverse reaction to the vaccine.”
He is one of about 90 Maryland residents participating in a clinical trial to see if diluted doses of the smallpox vaccine produce adequate immunity in adults who were previously vaccinated. There are part of a trial sponsored by the National Institutes of Health that involves seven study sites and a total of 920 people around the country.
“If we show one-to-five dilution of the vaccines works for those people who have been vaccinated and those who have not been vaccinated, we will have enough vaccines for the entire (U.S.) population,” said Dr. Margaret Rennels. She is lead investigator for the trial at the University of Maryland School of Medicine’s Center for Vaccine Development.
The Centers for Disease Control and Prevention Web site said that there are currently 15.4 million doses of smallpox vaccine available, and it will take years for accelerated production to boost that amount significantly. Dilution, if it works, would stretch the current stockpile of vaccine many times.
The latest study is a “follow study” to a 2001 NIH test of diluted vaccine on people who had never been vaccinated. Dr. Carol Tacket, the lead investigator of the earlier Baltimore study, found evidence that vaccines one-fifth to one- tenth as strong as the original are effective on those who were never immunized.
In the current study, previously vaccinated volunteers are divided into three groups. One group gets a full dose of vaccine, one gets a vaccine that is one-fifth as strong and the last gets a dose one-tenth as strong.
Most of the Maryland volunteers are employees of the university’s medical school, between the ages of 32 and 70. They will get $200 to $300 for participating, said Larry Roberts, a spokesman for the school.
Because the volunteers are members of the medical community, most are participating to contribute to scientific research, Roberts said.
On Tuesday, volunteers received vaccine that contains the live vaccinia virus, a “pox” type of virus related to smallpox. It is coated on the skin and then introduced with a bifurcated needle that pricks the skin 15 times in a few second.
Dudley said the poking is not deep and the procedure felt like “gently pushing a ballpoint pen” into the arm.
After the vaccine is given, it is immediately covered with gauze with a semipermeable dressing over it. There is a chance the virus could spread, but only if the bandage came off and the subject was in very close contact to another person, Rennels said.
Even so, Rennels and her team said they have taken every precaution to protect trial participants and those they come in contact with.
Before vaccination, each participant is educated about the trial and possible side effects. Each has to take a multiple-choice exam and get a grade of 70 percent or better to be eligible for the trial, Rennels said. Each is taught how to keep the vaccination site safe after vaccination.
Participants had to submit to a full review of their medical history, physicals and blood tests.
While vaccination is the best protection against smallpox, there are some risks associated with the procedure. The CDC has estimated that one or two people in every 1 million vaccinated for smallpox for the first time can die from the procedure.
Rennels said the reaction rate for people who have previously vaccinated is 10 times lower than that for first-time subjects, but there is still a chance a person could have a allergic reaction ranging from mild to severe.
Once vaccinated, a subject will develop a red, itchy bump develops with three to four days at the inoculation site if it was successful. The bump becomes larger and fills with pus, before beginning to drain in about a week. In the third week, the scab falls off and leaves a scar.
Routine smallpox vaccinations ended in 1972 and the disease was declared eradicated by the World Health Organization in 1980. Since last year’s terror attacks, however, federal and state governments have been taking steps to prepare in case smallpox is used as a weapon of bioterrorism by developing plans for mass vaccinations.
Dudley, who works at the medical school as a post-doctoral research assistant studying a derivative of e. coli, said he was motivated to participate in the Baltimore trial because he wanted to contribute to medical research. But he was also “curious.”
“I was immunized 33 years ago and I’m curious to see if I’m still protected,” he said. “Does my body still recognize the small pox virus, I wondered.”