Typhoid vaccine
The Typhoid vaccine is designed to prevent infection from the Salmonella enterica serotype typhi bacteria, particularly in regions suffering from poor sanitation. Typhoid fever, characterized by fever, rash, and malaise, is primarily transmitted through fecal contamination of food and water. Globally, there are an estimated 22 million cases and around 200,000 deaths annually, with a much lower incidence in the United States, mostly among travelers.
There are two main types of typhoid vaccines available: an intramuscular inactivated vaccine and an oral live attenuated vaccine. Both are effective in providing protection, though they do not guarantee 100% immunity. Vaccination is particularly recommended for travelers to high-risk areas, such as South Asia, and for those in contact with carriers of the bacteria.
While the vaccines are generally safe, mild side effects can occur, and certain individuals, particularly those with weakened immune systems, may face contraindications. Despite the vaccine’s benefits, it is essential for vaccinated individuals to continue practicing food and water safety measures while in areas with inadequate sanitation.
Typhoid vaccine
Definition
Typhoid vaccines prevent infection caused by Salmonella bacteria found in areas of poor sanitation worldwide.
Pathogen and Disease Characteristics
Typhoid fever, an acute illness of fever, rash, and malaise caused by S. enterica, serotype typhi (commonly known as S. typhi), is distinguished from typhus by its intestinal symptoms. Humans are the only source, and bacteria are spread through fecal contamination of food and water sources. An estimated 22 million cases of typhoid and approximately 200,000 deaths occur each year worldwide, but only 400 cases occur in the United States (primarily in travelers). Approximately 2 to 4 percent of people with acute fever become chronic carriers.
Vaccine Development and Descriptions
Early typhoid vaccines had numerous adverse effects, poor efficacy, or low potency. An inactivated injection and an oral attenuated version are now available and are active against strains of S. typhi, but even these are not 100 percent effective; approximately 50 to 80 percent of recipients are protected.
Typhim VI is an inactivated cell surface polysaccharide vaccine of S. typhi, Ty2 strain for intramuscular administration; it contains 0.25 percent phenol preservative, is safe for ages two years and older, and should be administered a minimum of two weeks before possible typhoid exposure. Boosters are recommended every two years if necessary.
Vivotif, an oral vaccine against typhoid, contains live attenuated virus from the Ty21a strain. The four-capsule regimen should be administered a minimum of one week before possible exposure; one capsule is taken every other day. Vivotif is safe for ages six years and older and should be swallowed whole with a cool liquid, one hour before a meal. Boosters should be given every five years. Both products require refrigeration at 2° to 8° Celsius (36° to 46° Fahrenheit) before use.
Vaccination Settings and Risk Groups
Vaccination is recommended for travelers to areas without proper sanitation, for persons who have contact with people who are carriers of S. typhi, and laboratory staff who work with pure typhoid culture. (Higher rates of fever are noted in these technicians.)
S. typhi is spread through unclean water sources in Africa, Asia, Central America, and South America. Disease risk is greatest for travelers to South Asia, for longer durations of travel, and for travelers visiting friends or family.
Adverse Effects and Contraindications
Typhoid vaccines are not recommended for common use in local populations of risk areas or for treatment of chronic carriers.
Vaccine side effects are mild and typically resolve within forty-eight hours. Adverse effects of fever, headache, injection site reaction (with intramuscular administration), and gastrointestinal upset causing reduced capsule absorption (with oral vaccine) occur in less than 10 percent of cases. Immune diseases may increase the risk of any adverse events.
Vaccine contraindications are acute febrile illness and previous allergic reaction (such as hoarseness, wheezing, and anaphylaxis) to the vaccine. Live vaccine should not be given to persons with a weakened immune system (such as from human immunodeficiency virus infection), to persons with cancer or who are undergoing cancer treatments, to persons receiving immunomodulating drug treatment or corticosteroid treatment for more than two weeks, and for persons receiving certain antibiotics, such as sulfonamides, within one day of a planned vaccination.
Impact
Typhoid incidence decreased dramatically with vaccine use and with improved sanitation and prevention measures. Because the vaccine is not 100 percent effective, vaccinated travelers should practice preventive measures, such as boiling raw foods, avoiding drinks with ice, and using only boiled or bottled liquids when traveling in countries without adequate sanitation.
Bibliography
“Immunization: Typhoid Vaccine.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John E. Bennett, and Raphael Dolin. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.
Levine, Myron M. “Typhoid Fever.” In Bacterial Infections of Humans: Epidemiology and Control, edited by Philip S. Brachman and Elias Abrutyn. 4th ed. New York: Springer Science, 2009.
‗‗‗‗‗‗‗. “Typhoid Fever Vaccines.” In Vaccines, edited by Stanley A. Plotkin, Walter A. Orenstein, and Paul A. Offit. 5th ed. Philadelphia: Saunders/Elsevier, 2008.
Nampota-Nkomba, Nginache, et al. "Using Typhoid Conjugate Vaccines to Prevent Disease, Promote Health Equity, and Counter Drug-Resistant Typhoid Fever." Open Forum Infectious Diseases, vol. 10, no. 1, 2 June 2023, doi: 10.1093/ofid/ofad022. Accessed 7 Feb. 2025.