Salmonella typhi is the bacterium that causes typhoid fever, an illness characterized by fever, fatigue, malaise, a lack of appetite, and often diarrhea. The bacteria are spread by direct contact with infected food or with an infected person’s stool. There are currently several excellent antibiotics for treating the more severe cases of typhoid fever. In the past, the fatality rate was around 30 percent. Antibiotic treatment has lowered that to around 1 percent. However, given that there are between twenty and thirty million cases of typhoid fever a year, the illness still kills tens of thousands of people annually.
There are two typhoid vaccines. The injectable vaccine is a killed polysaccharide vaccine that can be given to anyone over the age of two. Each injection lasts for two years. The oral vaccine is a live, attenuated-virus vaccine and can be given to anyone over the age of six. It is given in a series of four pills every other day for a week. This series lasts for five years. The side effects for both vaccines are uncommon and minimal when they do occur. Most adults prefer taking the oral vaccine, as it lasts longer and doesn’t involve a needle.
Neither vaccine should be given to anyone who has had a severe allergic reaction to a previous dose of the vaccine or to any component in the vaccine. Because the oral vaccine contains a live, attenuated virus, it is not recommended for any person with a deficiency of the immune system. This would include anyone who has HIV or certain kinds of cancer, is receiving chemotherapy or radiation therapy, or has been on medications that suppress the immune system, such as steroids, for more than two weeks. If a pregnant woman is a candidate for a typhoid vaccine, the injectable killed-virus vaccine is preferred over the live, attenuated, oral vaccine because of the theoretical risk that the attenuated virus could affect the fetus.
If there is no medical reason to not give the vaccine, we follow the CDC recommendations. If the CDC recommends this vaccine for a given country, then we also recommend this vaccine for a traveler to that country.