Filed at 5:49 p.m. ET

WASHINGTON (AP) -- A panel of scientists on Wednesday endorsed the safety and effectiveness of the anthrax vaccine, but also recommended research into improving it.

Last year's antrax-by-mail attacks focused additional attention on the vaccine, already criticized by some military members who resigned rather than take it because of concerns about side effects.

The study by the National Academy of Science's Institute of Medicine concluded that the vaccine protects against all forms of anthrax and has no more serious side effects than other vaccines given to adults.

``The anthrax vaccine should protect against even the inhalational form of the infection, but the lengthy vaccination schedule and the way the shots are physically administered make it far from optimal,'' said Brian L. Strom, chairman of the committee that reviewed the vaccine.

The committee urged the Defense Department to support research into a better vaccine.

The vaccine was approved by the Food and Drug Administration in 1970. The manufacturer, BioPort Corp., took over the product in 1998, but not until February did it win FDA approval for full production.

After the anthrax attacks, many postal workers and Senate employees were given protective antibiotics in case they had been exposed to anthrax. When those workers finished the first 60 days of antibiotics, medical experts suggested they could continue on those drugs, add vaccinations or end treatment. Most opted to avoid the vaccine.

Asked if he would have recommended they take the vaccine, Strom said the answer would be yes, if he had known then what he does now.

Bob Kramer, president of BioPort, said he is pleased that ``once again the safety and efficacy of the vaccine has been confirmed.''

The report was also welcomed by the Pentagon for ``confirmation that the department uses a protective measure that works for those at risk of exposure to the lethal agent anthrax,'' said Dr. William Winkenwerder Jr., assistant secretary of defense for health affairs.

But Steve Robinson of the National Gulf War Resource Center, said he will press the Defense Department to establish a mandatory compensation program for anyone who has a serious reaction to the vaccine.

The report said the rate of reactions was similar to that of other vaccines, such as tetanus, that were given to adults. These included skin redness, occasional malaise and muscle pain but no serious health impairments, the report said.

There is only limited information about possible long-term effects, the report noted, but there are no indications of increased risks.

But the vaccine is manufactured using older technology and requires six shots plus an annual booster, something the committee felt should be improved.

``The most prudent course of action is to develop a new vaccine -- given the nation's war against terrorism and the domestic attacks where anthrax was used as a deadly weapon,'' said Strom, director of the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania.

The current vaccine has been used to protect veterinarians and others who work with animals.

Normally anthrax is a disease of animals, and humans have contracted it from handling or working with the animals. Anthrax spores can live for years.

Five people died from the inhaled form of the disease, including two postal workers, after letters containing anthrax were sent to people in Florida, New York and Washington, D.C., last fall.

There are also skin and intestinal forms of the disease.

The academy is a private organization chartered by Congress to advise the government on scientific matters.

Also on Wednesday, FBI Director Robert Mueller told a House Appropriations subcommittee that the investigation is moving ahead on several fronts, both inside the United States and overseas.

``I will tell you that we have no one person specifically that stands out above others at this juncture,'' Mueller said. ``We are looking at, still looking at, a number of individuals.''

Sen. Chuck Grassley, R-Iowa, reported that the cost of cleaning up anthrax-contaminated congressional offices has reached $23 million.

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On the Net:

National Academy: http://national-academies.org/

BioPort: http://www.bioport.com

Food and Drug Administration: http://www.fda.gov

Defense Department: http://www.defenselink.mil/