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Public Health - Seattle & King County

Oral typhoid vaccine (Ty21a)

What is typhoid fever?

Typhoid fever is a disease caused by the typhoid bacillus, Salmonella typhi. It is spread through contaminated food and water or by close contact with an infected person. It occurs worldwide, and while uncommon in the United States, cases are reported every year, especially from travelers. The highest disease rates occur in Chile, Peru, India, Pakistan, Indonesia, Nigeria, and North Africa, and other countries where difficulties in sanitation and unprotected water supplies exist. Symptoms may include fever, headache, listlessness and body aches, loss of appetite, and stomach problems often beginning with constipation, followed by serious diarrhea. Symptoms can be severe and prolonged. In serious illness, 10 out of 100 infections (10%) may result in death. If treated with appropriate antibiotics, this may be reduced to less than 1%.

Oral typhoid vaccine (Ty21A)

Oral typhoid vaccine reduces disease incidence by 60-77%. Oral typhoid vaccine is recommended for adults and children six years of age or older for:

  1. Travel to areas which have high rates of typhoid fever or where food preparation, water treatment and sanitation are difficult.
  2. Intimate exposure to a known typhoid carrier, such as would occur with continued household contact.

Since typhoid vaccines cannot provide 100% protection, even vaccinated persons could get typhoid fever if exposed to high numbers of bacteria. Therefore, your best protection against typhoid is to avoid exposure by following recommendations for safe food and drink (e.g. drink only bottled or boiled water and eat only thoroughly cooked food served hot), and handwashing.

Immunization schedule

The oral typhoid capsules should be kept cold. They will usually remain cool enough on the way if kept away from direct heat and sun. As soon as possible, place the capsules in the refrigerator (at a temperature between 35° and 46° F.) Keep the vaccine capsules refrigerated until you finish all 4 capsules; if allowed to warm, the vaccine may become ineffective.

All four capsules must be taken to achieve the best protection. Take one capsule every other day. It will take seven days to complete. You should finish at least one week prior to possible exposure to typhoid fever. Take each capsule on an empty stomach, 1 hour before eating or 2 hours after a meal. Many have found it easiest to schedule the dosage around the evening meal. Swallow with a full glass of cold or cool water. The vaccine capsules should not be chewed and should be swallowed as soon after placing in the mouth as possible.

If you have continued or repeated exposure to typhoid bacteria, a booster dose (another series of 4 capsules) may be taken every five years.

*NOTE: If the typhoid capsules are left out of the refrigerator (more than 2 hours at room temperature), or if you place them in the freezer by mistake, put them in the refrigerator immediately and call our clinic. Ask to speak with the pharmacist about a prescription you received from our clinic.

Please consult with us if you are now receiving or will start taking antibiotics, or will begin antimalarial medicines while taking oral typhoid since these medicines may make the vaccine ineffective.

Possible side effects of the vaccine

Oral typhoid vaccine is well tolerated. If side effects occur, they are usually mild and brief. Common minor effects include a bloating or "queasy" feeling. Taking the capsule close to bedtime can often decrease this. Other rare reactions have included vomiting, abdominal cramps, loose stools, minor skin rash or itching, and fever or headache.

Interaction with other vaccines and medications

  • Certain antibiotics (including sulfonamides, amoxicillin, chloramphenicol, and ciprofloxacin) may interfere with oral typhoid vaccine. These medications should not be taken within 24 hours of oral typhoid vaccine capsules.
  • The antimalarial drugs mefloquine (Lariam) and chloroquine (Aralen) have been shown to not decrease the immune response to oral typhoid vaccine. However, the antimalarial drug proguanil (available in combination with atovaquone as Malarone in the United States) has been shown to decrease the immune response to oral typhoid vaccine and should be administered only if 10 days or more have elapsed since the final dose of oral typhoid vaccine was ingested.
  • There is no interference between oral typhoid and other vaccines.

When you should not take the vaccine

  1. During any illness with high fever or current illness of the gastrointestinal system (e.g. diarrhea). Persons who have active ulcer disease or other ongoing intestinal condition should first consult with their own physician before taking this vaccine.
  2. If you are immunosuppressed from illness or treatment, including:
    1. immune-deficiency disorders, such as agammaglobulinemia, HIV, AIDS
    2. leukemia, lymphoma, or generalized malignancy or cancers
    3. immune suppressive medications or treatments, such as cortisone drugs or radiation
    4. having recently received a transplant.
  3. If you have had an allergic reaction to a previous dose of oral typhoid immunization, or an allergic reactxion to any of this vaccine's components. However, a history of a severe reaction to past typhoid shots should not prevent you from taking the oral typhoid vaccine.

Effectiveness with children

While this is a very safe immunization, there are no current studies that show this vaccine is effective in children under 6 years of age. This is due in part to the difficulty for children under six to swallow capsules.

Use of oral typhoid vaccine during pregnancy or for breastfeeding mothers

Specific information concerning use of oral typhoid vaccine during pregnancy or for breastfeeding mothers is not available. However, it may be used when risk of exposure to typhoid fever is high.


If the person who received the vaccine experiences any of the side effects listed above and visits a doctor, hospital, or clinic after vaccination, please report it to the Health Department.