How is the Ty21a (typhoid vaccine) administered?

Administration of Ty21a Typhoid Vaccine

The Ty21a typhoid vaccine is administered orally as one enteric-coated capsule taken on alternate days for a total of four capsules, with each capsule taken with cool liquid no warmer than 37°C (98.6°F) approximately 1 hour before a meal. 1

Detailed Administration Protocol

• Dosage schedule: 4 capsules total, with one capsule taken every other day
• Administration timing: Each capsule should be taken approximately 1 hour before a meal
• Liquid requirements: Capsules should be taken with cool or lukewarm liquid that does not exceed body temperature (37°C/98.6°F)
• Storage requirements: The vaccine must be kept refrigerated between 2°C and 8°C (35.6°F - 46.4°F) at all times, including between doses 2

Important Administration Considerations

Proper Handling

• The capsule should be swallowed whole without chewing 2
• The capsule should be swallowed as soon as possible after placing in the mouth 2
• Unused vaccine must be returned to the refrigerator between doses to maintain potency 2

Contraindications

• Should not be administered during acute gastrointestinal illness 2
• Should not be given to individuals receiving sulfonamides or antibiotics, as these may be active against the vaccine strain 2
• Should be postponed if persistent diarrhea or vomiting is occurring 2
• Not recommended for immunocompromised persons, including those infected with HIV 1, 2

Drug Interactions

• Several anti-malarial drugs may interfere with immunogenicity:
  • Mefloquine and chloroquine can be administered together with Vivotif 2
  • Proguanil should be administered only if 10 days or more have elapsed since the final dose of Vivotif 2

Booster Recommendations

For continued protection under conditions of repeated exposure to S. typhi, revaccination is recommended:

• The manufacturer recommends revaccination with the entire four-dose series every 5 years 1
• Long-term follow-up studies have shown continued efficacy for up to 5-7 years after vaccination 3

Common Pitfalls to Avoid

1. Poor compliance with administration instructions: Studies show approximately 30% of travelers fail to follow one or more administration instructions, which may reduce vaccine effectiveness 4

2. Improper storage: Failing to keep the vaccine refrigerated between doses can compromise potency 2

3. Incorrect timing with meals: Taking the vaccine after meals rather than 1 hour before can reduce effectiveness 4

4. Concurrent antibiotic use: Administering the vaccine while the patient is taking antibiotics may prevent sufficient multiplication of the vaccine strain to induce a protective immune response 2

5. Inadequate completion of the series: All four doses must be taken to achieve maximum efficacy 1, 2

The Ty21a vaccine has been shown to be well-tolerated with minimal side effects, making it an attractive option compared to injectable typhoid vaccines 4. When properly administered according to the recommended schedule, it provides protection for at least 5 years with efficacy rates of 62-78% 3.