Since 1991 and the first Gulf War, the Defense Department has required service members to be immunized against such childhood diseases as Typhoid and Hepatitis A as well as against biological agents such as anthrax, when deploying to Korea or the Middle East.

But with Army officials reporting 1,200 illnesses and several thousand more queries about potential side effects, the Defense Department has started allowing troops deploying overseas to opt out of receiving the anthrax vaccine without penalty, according to the Army and Air Force.

Maj. Brian Blalock, public health flight commander at Nellis Air Force Base, said the anthrax shot is no longer mandatory for service members who are willing to sign a waiver releasing the military from liability. Still, the majority of service members elect to have the shot, he said.

"We've really not seen a big problem with anthrax -- nothing outside of the normal range of side effects," Blalock said.

Roughly 30 percent of men, and 60 percent of women, who receive the anthrax vaccine have some sort of minor reaction, such as swelling or a small lump at the injection spot, Blalock said.

But the illnesses reported by the Army have been more severe. Initial symptoms of the reported cases included minor diarrhea, cramping and fever to more intense problems like sleep and memory loss, chronic fatigue, headaches and chest pains.

Local numbers for service members affected are not available.

The national cases have been handled by the Vaccine Healthcare Centers, which are located at several U.S. military bases, but are overseen by the vaccination program at Walter Reed Army Medical Center in Washington D.C.

Despite the illnesses, Walter Reed officials contend that more than 1.3 million military and civilian personnel have received the vaccine since 1998 when the military began requiring members to receive a series of six shots to guard them against the anthrax virus.

The hospital contends anthrax vaccinations are safe and more necessary than ever, especially considering the threat of anthrax contamination that hit several post offices and office buildings following Sept. 11.

"We're living in a completely different era. There are terrorists who are intent on using biological agents and there are countries that certainly have the capability," Blalock said.

The military shut down the anthrax vaccination program temporarily prior to 1998 citing concerns about outdated versions of the shot. The necessity of the shot has been a hot point of debate in Washington and among soldiers' advocacy groups that contend illnesses from the vaccine have put some members out of the service.

Medical officials hope that educating service members about the benefits of getting the shots will encourage "across the board" compliance. They contend there is insufficient information to quantify the seriousness of illnesses resulting from the anthrax vaccine.

The Nevada National Guard, which routinely deploys members to Iraq and Afghanistan to fight the global war on terror, still requires the anthrax shot for soldiers and airmen going there or to Korea.

Spokeswoman Lt. April Conway said there have been no reported cases of adverse reactions to the shots among Guard members, but there have been some members who refused to have the vaccine.

"A couple years ago we had a few people who asked not to do it," Conway said. "Their positions were filled by volunteers who were willing."

Though military budget concerns may force the closure of the Vaccine Healthcare Centers which oversees assessment and treatment of anthrax-based problems, Congress and the Food and Drug Administration have approved an emergency use authorization to fund more of the anthrax vaccine.

Citing a renewed threat of anthrax poisoning to U.S. forces overseas, the Pentagon announced last month it would resume providing mass anthrax vaccinations for service members deploying to Korea or Southwest Asia.

While the debate about the seriousness of anthrax-related illnesses is likely to get bogged down in the same discussion over such war-related illnesses as Gulf War Syndrome, Blalock is among those who believe the benefits far outweigh the cost.

"There are a lot of diseases out there -- very lethal, very deadly," Blalock said. "It really comes down to people making the best choice."