WASHINGTON (AP) _ Pentagon officials came under sharp questioning Wednesday about plans to inoculate 2.4 million members of the armed forces against anthrax.

``Why this vaccine?'' Rep. Christopher Shays, R-Conn., asked at a hearing of the House Government Reform's subcommittee on national security.

Up to 200 service members have refused to take the vaccine. The Pentagon has said that 220,000 have been vaccinated.

``Anthrax is the primary biological warfare threat faced by U.S. forces,'' Sue Bailey, assistance defense secretary for health affairs, told the panel. She said the anthrax vaccine was tested by the Food and Drug Administration and found safe, a determination confirmed by an independent review.

``There have been no long-term side effects reported with the FDA-licensed anthrax vaccine,'' which has been in use since 1970, she said.

Shays said there was a lack of trust in the Pentagon program and he said the military's efforts to counter concerns ``seem heavy-handed and one-sided, glossing over legitimate concerns about the safety and efficacy of the vaccine, minimizing adverse reaction reports, and blaming the Internet for fanning dissent.''

Also testifying were many critics of the mandatory policy adopted by the Pentagon.

``We are jumping from vaccinating 150,000 in the Gulf War to 2.4 million on shaky ground,'' said Col. Redmond Handy, a reserve officer.

``By implying we are protected from anthrax may place many soldiers in more danger,'' said Capt. Thomas Rempfer, who quit the National Guard after completing a report on the anthrax vaccine.

It was the first of several hearings the committee plans on this issue and the committee plans to call the FDA to testify next.

``We will follow it until we are sure medical force protection means assuring the long-term health of U.S. forces not just short-term mission capability,'' Shays said.