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Smallpox Vaccination Program Safe

Few Side Effects Reported in Large-Scale Military Vaccination Program

WebMD Health News

June 25, 2003 -- Large-scale smallpox vaccination programs can be carried out safely, according to new research from the U.S. military.

Although concerns regarding potentially dangerous complications caused by the smallpox vaccine have emerged in recent months, researchers say the military's smallpox vaccination program had lower than expected rates of serious side effects.

A nationwide smallpox vaccination program began in December 2002 for key military and State Department personnel and emergency health-care workers. In March, the CDC announced that people with heart disease would no longer be eligible for smallpox vaccination after several reports of heart problems and at least one death were linked to the smallpox vaccine.

In a study published in The Journal of the American Medical Association, researchers say the Department of Defense vaccinated more than 450,000 military personnel from Dec. 13, 2002 until May 28, 2003 at a variety of locations. Vaccination was required for all troops except pregnant women or those with skin conditions or immune disorders that are not recommended for vaccination due to a risk of complications.

Researchers found that between .5% and 3% of people who received the vaccine needed short-term sick leave for vaccine-related illness, such as fever, usually eight to 12 days after vaccination. Most required only one day of sick leave.

"Our experience suggests that broad smallpox vaccination programs may be implemented with fewer serious adverse events than previously believed," write the researcher John Grabenstein, R.Ph, PhD, of the U.S. Army Military Vaccine Academy in Falls Church, Va., and colleagues.

Overall, rates of adverse events were generally lower than those found during past vaccination efforts. Once case of encephalitis (inflammation of the brain) and 37 cases of inflammation of the heart occurred, but all cases recovered.

Another study published in the same journal examined the first cases of inflammation of the heart that occurred during the military smallpox vaccination program. Although only four cases of this condition had been reported from 1955 to 1986, defense department researchers say it should be considered an "expected but apparently uncommon adverse event associated with smallpox vaccination."

In addition, a third study in JAMA, found that smallpox vaccination is also safe and effective among persons who have not received the vaccine in the past. Researchers tested both the full-strength smallpox vaccine and various diluted versions among 80 people who had not previously been vaccinated.

The study found 95% of the participants had a successful immune reaction to the undiluted smallpox vaccine. Only 3%-7% developed either a generalized or local rash from the vaccination, all of which resolved without scarring and were found to be negative for vaccinia, the virus that can be caused by the vaccine itself.

In another study also in this issue of JAMA, previously vaccinated adults were shown to have fewer skin reactions and incidences of fever after smallpox vaccination than those who had received the vaccine for the first time. Antibody responses, which signal that the vaccine is protecting the body against disease, also occurred faster and at higher rates than found among previously unvaccinated adults.

The smallpox vaccine is expected to become available to the general public by 2004.

SOURCE: The Journal of the American Medical Association, June 25, 2003. WebMD Medical News: "Heart Issues Linked to Smallpox Vaccine," "President Offers Smallpox Vaccine to All."

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