President Bush, following through on a startling vow he made a week earlier, was vaccinated against smallpox in private yesterday and showed no immediate side effects, the White House said.

The military began administering 500,000 smallpox inoculations this month, and Bush said he took the shot in his role as commander in chief but does not recommend it for the general public.

"He understands there are a lot of things we ask our military to do that the commander in chief doesn't do," a senior administration official said. "But he felt this was unique and thought it would send a good signal to the troops -- that he understands the sacrifices that they make."

The official said Bush's decision was also an effort to head off a repeat of the resistance among some members of the military to anthrax vaccinations after the terrorist attacks of Sept. 11, 2001.

Routine smallpox vaccinations were discontinued in the United States in 1972, and the virus, deadly and highly contagious, was declared eradicated in 1980. But the war on terrorism has revived government fears about its use as a biological weapon. United Nations weapons inspectors have investigated whether Iraq has tried to turn the virus into a weapon.

The administration is suggesting the shots for medical professionals and emergency workers who could come into contact with smallpox. It plans to make the vaccine available by summer to healthy American adults who want it. But the administration is discouraging inoculations for the general public because of the potential side effects, which can be fatal.

Administration officials announced Bush's vaccination after he arrived at Camp David, where he will remain through Christmas. Bush was vaccinated in the White House's medical unit, an official said.

News organizations were not invited to photograph the vaccination, and the official said that was to avoid undermining the message that health and national security experts do not believe vaccination is necessary for the general public.

Bush said on Dec. 13 that his staff and his family would not get the shot.