July 11, 2003

Study tests smallpox vaccine bandages

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Photo by Dana Johnson

Study tests smallpox vaccine bandages

As questions continue to swirl around President Bush’s national smallpox vaccination plan, Vanderbilt University Medical Center is launching a new smallpox bandage trial that will help answer questions about one of the major issues associated with receiving the vaccine.

In addition to vaccine side effects experienced by some individuals, another significant concern with the President’s national vaccination plan is the risk of individuals who have been vaccinated may transmit the vaccinia virus, the cowpox virus used in the vaccine, to others.

With the chance of spreading vaccinia virus to an at-risk patient population many U.S. hospitals, including VUMC, have chosen to wait until the threat of disease is imminent before vaccinating their staff.

VUMC’s latest smallpox vaccine study will examine the effectiveness of three different types of bandages and their ability to contain virus shed from the vaccine site.

Two previous smallpox vaccine studies at VUMC were conducted to determine whether decades-old vaccine is still viable, even when diluted, and to determine a dilution of the vaccine that still remains effective.

A sub-study of VUMC’s second smallpox vaccine trial examined the effectiveness of one type of bandage at containing the virus.

“With this vaccine we set up an infection on the patient’s arm, which is unlike any other vaccine we give. The patient gets an active viral response to a virus that’s a cousin of smallpox. The risk is that this virus on the vaccine site can be transmitted to others and cause infection,” said Dr. Tom Talbot, instructor in Medicine in the Division of Infectious Diseases. “The vaccinia virus is not as virulent as smallpox, but the risk is always there.”

Since activation of the President’s smallpox vaccination plan there have been newly documented cases of vaccinia virus being transmitted to others by vaccinated individuals. Infectious disease specialists warn there are many more individuals who are at risk for severe complications from an unwanted infection than ever before.

Individuals with skin diseases such as eczema or psoriasis, whose immune system is not working normally, or individuals with AIDS/HIV are at increased risk.

“In the two previous studies we used a layer of gauze and a double-occlusive bandage on top of that over the vaccine site. In the second study we performed a culture study consisting of culturing the index finger on the hand opposite the arm of the vaccine site, an area on the outside of the bandage, and the actual vaccine site itself as a control,” said Talbot.

“With the double-occlusive bandage we found a very low rate of recovery for the vaccinia virus. Only six of 917 bandages cultured proved positive. That’s a recovery rate of less than 1 percent for the bandages.

“On the 925 hand cultures we collected there were only two positive specimens. What this tells us is that these bandages are very protective.”

Talbot also attributes the extremely low presence of vaccinia virus outside the bandages to excellent secondary education about dressing changes and proper hand washing.

Current Centers for Disease Control and Prevention (CDC) policy calls for healthcare workers receiving the smallpox vaccine to also receive double-occlusive dressings. Current practice for individuals who are not healthcare workers who receive the vaccine calls for the use of ordinary gauze held in place by tape.

“There is concern the double-occlusive bandage system actually slows down healing at the vaccine site. The normal process after someone receives the vaccine is for a scab to form, and then it dries and falls off. The individual is then no longer infectious,” said Talbot.

“The occlusive bandage seems to keep the vaccine site moist and weeping virus longer, and may slow down healing. There is discussion among individuals who use this type of dressing whether the protective benefit of using the double-occlusive dressing is worth the longer healing time.”

Talbot says the study will seek to answer questions about healing time, and examine the effectiveness of two other bandaging methods at containing the virus.

“There is also a big cost differential associated with double-occlusive bandages, he said. “Our study will answer the question of whether this type of dressing is worth the cost.”

For the first time at VUMC this study will be including individuals older than 32 who received the smallpox vaccine when it was routinely given in the 1950s, 60s and 70s. Enrollees in the two previous studies were all under the age of 33 and were vaccine “naïve” having never received the vaccine.

Study participants will all receive an undiluted dose of smallpox vaccine so every participant has the chance to develop a uniform sore at the vaccine site.

“After receiving the vaccine, participants will be randomized to receive one of three different bandage types. They will either receive simple gauze and tape, a single-occlusive bandage with gauze, or a hydro polymer bandage resembling a very large waterproof Band Aid that is very occlusive, and also expensive,” he said. “The hydro polymer bandage is more expensive than using double-occlusive bandages, but are they more effective?”

As with the previous bandage study, participants will be required to make regular return visits so their vaccine sites, bandages, and hands can be cultured. Their bandages will be changed as well.

“From the previous study we know the double-occlusive bandages are extremely effective. What we’ll be able to tell now is how all these dressings will compare. The big question is how effective the gauze bandage will be at containing the virus, and what effect on healing time the various dressing may have.

“We hope to provide contemporary information in today’s world that will assure the community that these are very protective bandages, and that with proper infection control the risk of spreading the disease is minimal,” he said.

Healthy adults between the ages of 18 and 32 who have never been vaccinated for smallpox, and healthy adults between the ages of 33 and 49 who have previously been vaccinated for smallpox are eligible for enrollment.

Contact the Smallpox Trials Hotline at 343-8288 for more information. n