What is the dosage of Ty21a vaccine used in the prevention of typhoid fever (enteric fever)?

Updated: Aug 19, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

In the United States, primary vaccination with Ty21a consists of one enteric-coated capsule taken on alternate days to a total of 4 capsules. The capsules must be refrigerated (not frozen), and all 4 doses must be taken to achieve maximum efficacy.

The optimal booster schedule has not been determined; however, the longest reported follow-up study of vaccine trial subjects indicated that efficacy continued for 5 years after vaccination. The manufacturer recommends revaccination with the entire 4-dose series every 5 years if continued or renewed exposure to S typhi is expected. This vaccine may be inactivated if given within 3 days of antibiotics.


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