“There are a fairly large number of troops that have been identified as being the highest priority,” Dr. William Winkenwerder, assistant secretary of defense for Health Affairs, said in a televised interview Friday.

The interview followed President Bush’s public announcement to begin the smallpox vaccination program.

Troops on emergency response teams, military medical personnel and troops deployed to the front battle lines and to high-risk areas of the globe will be tapped for the vaccine, Winkenwerder said.

For security reasons, those high-risk areas are not being publicly identified. Guardsmen and reservists also will be vaccinated, he said.

While deemed safe, the vaccine produces side effects officials have said can be deadly. And while the program is mandatory, some servicemembers with health conditions will be exempt, including those with compromised immune systems such as HIV, skin conditions like eczema or cancer patients, he said. Women who are pregnant or recently gave birth also will be exempt.

Military health professionals have received the necessary training to begin inoculating troops with the vaccine, which hasn’t been used since 1972, when the disease was deemed eradicated.

The decision to vaccinate the troops was not made in a vacuum, Winkwerder said. The administration consulted with medical experts both in the United States and around the world for the best advice.

The decision of whether to vaccinate families of troops living in countries that might be targeted has yet to be made, he said.

Typically, the policy is to evacuate families in high-threat areas when the need arises. However, because of the lethality of smallpox and the ease in which it can be spread, officials are analyzing whether to vaccinate families.

Before getting the vaccine, personnel will go through an aggressive screening process followed by careful monitoring. Eventually, a telephone hotline will be set up for troops seeking information or to report side affects.