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Typhoid fever is caused by ingestion of food or water contaminated by a species of Salmonella known as Salmonella typhi. The organism may persist in the stool after signs of illness have resolved and may be passed to others if personal hygiene is poor, especially if the individual is involved in preparing food. The incubation period usually ranges from one to two weeks, but may be as long as two months. Fever occurs in virtually all cases. Other symptoms may include headache, malaise, muscle aches, dizziness, loss of appetite, nausea, and abdominal pain. Either diarrhea or constipation may occur. Possible complications include intestinal perforation, intestinal bleeding, confusion, delirium, or rarely coma. Because reports of resistance to older antibiotics are becoming more frequent, typhoid fever is usually treated with one of the quinolone antibiotics, such as ciprofloxacin or levofloxacin, generally by mouth. An alternative drug is ceftriaxone, which must be given by injecton.
Typhoid vaccine is generally given in an oral form (Vivotif Berna) consisting of four capsules taken on alternate days until completed. The capsules should be kept refrigerated and taken with cool liquid. Protection is achieved seven days after the last dose. Side-effects are uncommon and may include abdominal discomfort, nausea, and rash or hives. Oral typhoid vaccine should not be taken with antibiotics, because they may interfere with its effectiveness. If all four doses are not taken, the entire series must be restarted to achieve protection.
The alternative is an injectable polysaccharide vaccine (Typhim Vi; Aventis Pasteur Inc.) (PDF) given as a single 0.5 cc intramuscular injection. Immunity is conferred seven days after vaccination. Adverse reactions, which are uncommon, may include discomfort at the injection site, fever and headache. In February 2005, the manufacturer announced a temporary shortage of the injectable vaccine, which it attributed to increased demand and which it expected to last until early April 2005.
The oral vaccine is approved for travelers at least six years old, whereas the injectable vaccine is approved for those aged two or above. A liquid formulation of the oral vaccine has been shown to be effective in children as young as two years old, but has not yet been approved in the United States. The efficacy of both vaccines appears comparable, generally 50-70% in different studies. Boosters are recommended after five years for the oral vaccine and two years for the polysaccharide vaccine.
The safety of typhoid vaccine during pregnancy is unknown. If typhoid immunization is necessary during pregnancy, the injectable polysaccharide vaccine (Typhim Vi) is probably preferable, because it does not contain live bacteria. Oral typhoid vaccine is safe in HIV-infected individuals as long as their CD4 lymphocyte counts remain above 200.
Breastfeeding is probably protective against typhoid fever in infants.
Because the efficacy of typhoid vaccine is limited and because many other infections can be acquired from contaminated food and beverages, immunization against typhoid does not in any way diminish the importance of following food and water precautions.
From the World Health Organization (WHO)
Typhoid fever fact sheet
Typhoid and paratyphoid enteric fevers
Safety of typhoid vaccines
Typhoid vaccines (PDF) (WHO position paper)
From the Centers for Disease Control (CDC)
Typhoid Fever (Yellow Book)
Typhoid Fever: Frequently Asked Questions
Technical Information on Typhoid Fever
Typhoid Immunization: Recommendations of the Advisory Committee on Immunization Practices (PDF) (comprehensive discussion; chiefly for physicians)
From Health Canada
Statement on overseas travelers and typhoid fever
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