WASHINGTON (Reuters Health) Mar 06 - While the current US anthrax vaccine appears safe and effective, government agencies and private companies should speed efforts to develop easier-to-use vaccines, an expert panel concluded in a report issued Wednesday.

The Institute of Medicine (IOM), a scientific group that advises the federal government, concluded the vaccine appears effective in preventing inhalation anthrax, the illness that killed five people last October after a rash of anthrax-containing letters in the US. It also concluded that the vaccine is likely to work even against anthrax spores that are "weaponized" through genetic engineering to be more infective.

But the currently available vaccine requires six shots given over 18 months, a regimen that most experts consider impractical for public use. The IOM panel recommended that government agencies step up efforts to develop a vaccine in pill form or at least one that is effective with fewer shots. They also recommend that long-term studies be conducted on vaccine safety.

"It is sufficiently safe to be useful. Still, its side effects, coupled with the long series of doses required, are among the realities that underscore the need for a new and improved alternative," said Dr. Brian L. Strom, chair of the panel and director of the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania School of Medicine.

More than 2 million military personnel have received the anthrax vaccine since 1998, when the Defense Department instituted a policy of universal vaccination in the armed forces. Military planners became concerned during the Gulf War in 1991 that US personnel could be at risk of anthrax attack during combat.

The overall safety and effectiveness of the vaccine took on greater urgency for the public last October when five people died and more than a dozen were sickened after exposure to anthrax spores via the contaminated letters.

Nearly 200 civilians, mostly on Capitol Hill, received anthrax vaccinations following the attacks as a supplement to antibiotic drugs designed to prevent infection after exposure. US officials say that they have no plans to vaccinate members of the public in anticipation of further attacks.

The usefulness of the vaccine for post-exposure prevention is clear, according to Strom. "If that kind of event happened again and someone asked me should I take the vaccine, my answer would be yes," he said.

Still, the safety of the anthrax vaccine has caused some worry in the military. Some 400 armed forces personnel refused to comply with Pentagon orders for mass vaccination because of fears that the vaccine contributed to illnesses like those seen in Gulf War syndrome.

But studies of vaccinated servicemen and women found no unexpected risk of serious illnesses after vaccination, according to the IOM committee. Skin redness and soreness at the site of injection were common, occurring in one third to one half of all recipients based on findings from one study. More serious reactions, including fever and malaise, were far less common.

"There is no evidence that life-threatening or permanently disabling immediate-onset adverse events occur at higher rates in individuals who have received (anthrax vaccine) than in the general pollution," the report states.

Accurate studies of effectiveness are impossible to perform because they would require vaccinated people to be deliberately exposed to anthrax. Observational studies in the 1960s and 1970s suggest that a complete vaccine course protected textile mill workers from becoming infected with inhalation anthrax.

Today, concerns have also been raised about BioPort, the Michigan-based company holding the military contract to make anthrax vaccine. The Pentagon's vaccination program was slowed last year when BioPort was forced to refit its factory in order to comply with Food and Drug Administration (FDA) manufacturing guidelines.

FDA re-licensed the company at the end of January 2002, and concerns now abound that vaccine produced before the refit could differ in safety and effectiveness from vaccine produced afterward. Experts said that production at BioPort's facility has been "fraught with difficulties."

Bioport officials said that they are working to develop more convenient forms of anthrax vaccine, but that vaccine in pill form is unlikely to come soon. "It is likely that these vaccines will still require injections," said Robert Myers, BioPort's executive vice president.

The Centers for Disease Control is currently funding a study designed to test the effectiveness of simpler vaccine dosing regimens.