And now comes a report it could possibly be dangerous.
The San Diego Union-Tribune cites military documents that include a memo by Army Secretary Louis Caldera. He writes the vaccine involves "unusually hazardous risks" associated with the potential for adverse reactions, and that it may not provide the "desired immunological effect" in all recipients.
The Pentagon has insisted the vaccine is safe. Even so, about 200 military members have refused it, citing concerns about side effects.
Two Marines in California were convicted of disobeying a lawful order for refusing the shots Monday.
Lance Cpl. Michael McIntyre was given 30 days in confinement and a bad-conduct discharge. Lance Cpl. Jared Johnston received 25 days in confinement and also got a bad-conduct discharge.
The courts-martial completed prosecutions of five Marines in Twentynine Palms, California, who refused to take the vaccine. All were convicted.
The Pentagon says more than 220,000 members of the military have taken the anthrax vaccine, while about 200 have refused. More than 40 of the people who got the shot reported side effects, but all recovered.