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Health care workers with HIV or a history of atopic dermatitis are at real risk of serious complications if they receive smallpox vaccine. But can they be safely screened out if — as appears imminent — 500,000 hospital workers are offered smallpox immunization?
"The Israelis estimated in the past that they could reduce — by very rigorous screening — about two-thirds of severe adverse events," says Walter Orenstein, MD, director of the national immunization program at the Centers for Disease Control and Prevention. "But I emphasize that there still will be severe adverse events. There are events for which we have no risk factor — such as post-vaccinial encephalitis — which could be extremely severe. No screening system can perfectly eliminate all of these severe adverse events."
Still, most of the cases of post-vaccinial encephalitis historically have occurred in young children who, of course, would not be offered vaccine under a CDC proposal to vaccinate teams of key medical personnel in the nation’s hospitals.
Recently approved by the CDC’s Advisory Committee on Immunization Practices (ACIP), the recommendations were awaiting a final go-ahead by the federal government. When finalized as expected sometime in December, according to a Bush administration official, the key to preventing as many adverse events as possible will be a thorough screening process for contraindications to smallpox vaccine. "I think the numbers [of adverse events] would be reduced if the screening recommendations are implemented well," says John Modlin, MD, ACIP chairman. "How well that will go on is difficult to say, certainly. But I think it would [lead to] a marked decrease."
Following the initial vaccination of some 500,000 health care workers, the federal plan calls for a second wave of vaccinations for 7 million to 10 million more health care workers, firefighters, police, and first responders, according to a recent CNN report. The vaccine also would be made available to the public, through voluntary participation in clinical trials.
Fortunately, a large number of health care workers are old enough to have been immunized before the smallpox mass inoculation programs were stopped in the United States in 1972. Prior experience with the vaccine shows that those with a history of smallpox vaccination are less likely to have adverse reactions upon revaccination.
"It was the sense of the committee that for most programs it would be wise to initially begin with older health care workers who have a history of having been immunized in the past, to further reduce the likelihood of adverse events," Modlin says. "It is important to develop sufficient experience with these things [before] you begin to immunize younger health care workers who, as primary vaccinees, we know will be at higher risk of having adverse complications."
While those contraindicated should not be immunized in the "pre-attack" program that has been recommended by the CDC, workers in the various risk groups would face a different situation should a smallpox attack actually occur. Essentially, no one is contraindicated for smallpox vaccine if the disease, which has a mortality rate of about 30%, began spreading.
"Once you have a confirmed case of smallpox, all bets are off," says William Sheckler, MD, a member of the CDC Healthcare Infection Control Practices Advisory Committee who advised ACIP on the recommendation.
The list of those who should not receive smallpox vaccine pre-attack includes women who are pregnant or are trying to conceive. Before vaccination, women of childbearing age should be asked if they are pregnant or intend to become pregnant in the next four weeks, the committee recommended. "Women who respond positively should not be vaccinated," Modlin says. "In addition, women who are vaccinated should be counseled not to become pregnant during the four weeks after vaccination."
However, the committee did not go as far as recommending routine pregnancy testing of all women of childbearing age prior to immunization. Also, ACIP did not recommend mandatory HIV testing prior to smallpox vaccination; but the committee recommended that HIV testing should be "readily available" to all those considering smallpox vaccination. Health care workers who are HIV-positive or have developed AIDS are at increased risk of progressive vaccinia or vaccinia necrosum following smallpox vaccination.
Before vaccination, workers volunteering for the smallpox care team should be educated about the risks of severe complications from smallpox vaccine if they have HIV infection or other immunosuppressive conditions. HIV testing is recommended for those who have any history of a risk factor for HIV infection and who are not sure of their HIV infection status.
Issues of confidentiality inevitably arise, particularly given the historic stigma faced by health care workers with HIV infection. "The only way this will work is if it is totally voluntary," Sheckler says.
"The reasons for not [being vaccinated] do not have to be disclosed to the hospital. We don’t anticipate that there is any need for that information. Obviously the HIV situation is the most sensitive." In addition, people who have ever been diagnosed with eczema or atopic dermatitis should not be vaccinated, even if the condition is not currently active.
"I think the concern that we have is people who will develop what is called a generalized eczema [reaction], " Orenstein says. "So if they’ve got a past history of atopic dermatitis, and even if that has been mild in the past, the concern is that with vaccinia or smallpox vaccine, they can get total body involvement [over] large sections of their body."
There should be an initial staff meeting at the hospital to begin the education and informed-consent process, says Sheckler, epidemiologist at St. Mary’s Medical Center in Madison, WI. The meeting should include the hospital infection control professional, epidemiologist, and local public health officials who will review the contraindications of vaccination with the members of the medical, nursing, and auxiliary staff who would be candidates for the smallpox care team, he advises. "This meeting would be to discuss the vaccine, the contraindications, and the whole plan. Part of the advantage of having a preliminary informed-consent process is giving people the time to think about things, and also to make sure that they have access to pregnancy tests and HIV tests," Sheckler says. "The second step would be to get informed consent in advance of any vaccination. I think the major barrier is a history of atopic dermatitis or eczema. Some of the data from Wisconsin suggest that about 5% of adults have that diagnosis."
He estimates contradictions among workers and/or their household contacts will eliminate about 20% of possible hospital team members. In general, health care workers should rule out the vaccine if they have a household contact who has any of the contraindicating conditions.
"For example, if a health care worker has a child in the home with eczema, then that worker should not be vaccinated," Orenstein says. "If the worker has a household contact with severe immune-suppressive illness, then that worker should not be vaccinated. The same kinds of contraindications that are considered for people in vaccination would be applied also to household contacts since the vaccine virus — vaccinia — can be transmitted."
Following smallpox vaccination, health care workers involved in direct patient care should keep their vaccination sites covered with gauze or a similar absorbent material in order to absorb exudates that develop, ACIP recommends. That dressing should be covered with a semipermeable dressing to provide a barrier to vaccinia virus. Hospitals should form a site-care team to assess dressings for all vaccinated health care workers daily (whether involved in direct patient care or in other duties), determine if dressings need changing, and then change the dressing if indicated.
"With occlusive dressings and a team inspecting dressings, there is very good evidence that you have minimized to almost zero the risk of spreading it to someone else," Modlin says. "The best information we have, and that of course is from vaccination of health care workers in past decades, is that the risk of transmission of vaccinia virus in the hospital setting is extremely low. A greater concern would be risk of transmission not in the health care setting, but from a health care worker to someone who might be vulnerable in the household."
Smallpox vaccine may be administered at the same time as any inactivated vaccine, including influenza vaccine. With the notable exception of varicella (chickenpox) vaccine, smallpox vaccine may be administered simultaneously with other vaccines that contain live viruses. To minimize the clinical impact of inadvertent inoculation, ACIP recommends that all people who administer smallpox vaccine be vaccinated beforehand.
"The question of who is actually going to do the vaccination is hugely important as to how the local vaccine programs are going to work," says William Schaffner, MD, a liaison member of ACIP and chairman of the department of preventive medicine at Vanderbilt University School of Medicine in Nashville, TN.
"Hospitals operate seven days a week, 24 hours a day. If the health department does all the vaccinating, all the burden will fall on the hospital to get these people in, pay them extra [etc.]. If we permit our own people to do the vaccination that will be much more efficient, and we will have educated all of these [hospital] people on how to do the vaccination," he says.
Regardless of who does the vaccinating, the health care team members should receive immunization over staggered time intervals to minimize staffing problems due to reactions. Administrative leave is not required for newly vaccinated health care workers unless they are physically unable to work due to systemic signs and symptoms of illness or, if they do not adhere to the recommended infection control precautions, ACIP recommended.
"We anticipate that the administrative leave issues are more likely to come up somewhere between day seven and 10 after the vaccination," Schaffner says. "That is the period of time when the vaccinees are going to feel fever, chills and malaise."
(Editor’s note: If you have any questions about whether someone should receive the smallpox vaccine, visit the CDC web site at www.cdc.gov/smallpox.)