One of two forms of vaccine against typhoid fever. Attenuated (weakened) live virus is used for an oral vaccine taken in four doses by adults and children over age 6; it provides protection for 5 years. This vaccine should not be given to persons taking antimicrobial drugs or to those with AIDS. A parenteral type of the vaccine, made from the capsular polysaccharide of Salmonella typhi, given to children at least 6 months old, requires two doses 4 weeks apart, is effective 55% to 75% of the time, and lasts 3 years.