Usage
- Medical Conditions: Purified Vi Polysaccharide Typhoid Vaccine is prescribed for active immunization against typhoid fever caused by Salmonella enterica serovar Typhi (S. Typhi). This is particularly important for individuals traveling to endemic areas, residents of endemic zones, individuals in close contact with typhoid carriers, and laboratory workers handling S. Typhi.
- Pharmacological Classification: Vaccine, Immunizing Agent
- Mechanism of Action: This vaccine stimulates an immune response by inducing the production of antibodies, primarily IgG, against the Vi capsular polysaccharide of S. Typhi. This immune response helps protect against typhoid fever.
Alternate Names
- Typhoid Vi Polysaccharide Vaccine
- Typhoid Vi Vaccine
- Brand Names: Typhim Vi, Typbar-TCV
How It Works
- Pharmacodynamics: The vaccine triggers the body’s immune system to produce antibodies against the Vi antigen of S. Typhi. These antibodies bind to the bacteria, marking them for destruction by other immune cells. The vaccine primarily generates IgG antibodies.
- Pharmacokinetics:
- Absorption: Administered intramuscularly (IM) or subcutaneously (SC). The Vi polysaccharide is slowly absorbed from the injection site.
- Metabolism: Minimal metabolism of the polysaccharide occurs.
- Elimination: The elimination pathway is not well-defined, but it’s thought that the polysaccharide is gradually degraded. Excretion in breast milk is unknown.
- Mode of Action: The vaccine’s Vi polysaccharide acts as an antigen, triggering a T-cell independent B-cell response. This leads to the production of antibodies specific to the Vi antigen. It doesn’t directly bind to receptors, inhibit enzymes, or modulate neurotransmitters, but rather acts as an immunological trigger.
Dosage
Standard Dosage
Adults:
- A single 0.5 mL dose IM or SC.
Children (2 years and older):
- A single 0.5 mL dose IM or SC.
- Not recommended for children under 2 years, as antibody response may be inadequate.
Special Cases:
- Elderly Patients: Standard adult dose.
- Patients with Renal Impairment: Standard adult dose.
- Patients with Hepatic Dysfunction: Standard adult dose.
- Patients with Comorbid Conditions: No specific dosage adjustments are routinely recommended. Assess benefit vs risk for immunocompromised patients.
Clinical Use Cases
- The purified Vi polysaccharide typhoid vaccine is primarily for pre-travel or pre-exposure prophylaxis and not typically used in acute clinical settings like intubation, surgical procedures, mechanical ventilation, or the ICU. Its role is preventative rather than therapeutic.
- Emergency Situations: This vaccine is not for emergency use in acute typhoid fever cases.
Dosage Adjustments
- Immunosuppression may reduce the immune response. Postpone vaccination until the end of immunosuppressive therapy if possible.
Side Effects
Common Side Effects:
- Injection site reactions (pain, redness, swelling)
- Headache
- Myalgia
- Fatigue
- Fever
- Malaise
Rare but Serious Side Effects:
- Allergic reactions (anaphylaxis, rash, urticaria, angioedema, difficulty breathing, hypotension)
- Serum sickness
Long-Term Effects: No significant long-term side effects associated with the vaccine.
Contraindications
- History of severe allergic reaction to any component of the vaccine (including trace residuals like formaldehyde and casein)
Drug Interactions
- Immunosuppressants (e.g., corticosteroids, chemotherapy, radiotherapy) can reduce the immune response to the vaccine.
- Concurrent administration with other vaccines is generally acceptable, but administer at separate injection sites. No clinically significant interactions with specific medications are known.
Pregnancy and Breastfeeding
- Pregnancy: Not routinely recommended, but may be administered if the risk of typhoid is high and benefits outweigh the potential risks. Data on use in pregnant women are limited.
- Breastfeeding: Excretion in breast milk is unknown. Caution should be exercised.
Drug Profile Summary
- Mechanism of Action: Stimulates antibody production against S. Typhi Vi antigen.
- Side Effects: Commonly local reactions at injection site; rarely, severe allergic reactions.
- Contraindications: Hypersensitivity to vaccine components.
- Drug Interactions: Immunosuppressants may reduce immunogenicity.
- Pregnancy & Breastfeeding: Use with caution if benefits outweigh risks.
- Dosage: Single 0.5 mL dose IM or SC for adults and children ≥2 years.
- Monitoring Parameters: Observe for allergic reactions.
Popular Combinations
- May be co-administered with other travel vaccines (e.g., hepatitis A, yellow fever, meningococcal) at separate sites.
Precautions
- General Precautions: Screen for contraindications and previous reactions to vaccines.
- Specific Populations:
- Pregnant Women: Assess benefit vs. risk.
- Breastfeeding Mothers: Exercise caution due to unknown excretion in milk.
- Children & Elderly: Standard dose for those ≥2 years.
- Lifestyle Considerations: No specific lifestyle considerations.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Purified Vi Polysaccharide Typhoid Vaccine?
A: A single 0.5 mL dose IM or SC for adults and children 2 years of age and older.
Q2: How long does protection last after vaccination?
A: Protection typically lasts approximately 3 years.
Q3: Can this vaccine be given to infants?
A: No, it is not recommended for children under 2 years old.
Q4: What are the common side effects?
A: Common side effects include pain, redness, and swelling at the injection site, headache, myalgia, fatigue, and fever.
Q5: Are there any serious side effects?
A: Rarely, severe allergic reactions can occur.
Q6: Can pregnant or breastfeeding women receive this vaccine?
A: It is not routinely recommended for pregnant or breastfeeding women, but it can be given if the benefits outweigh the potential risks after careful assessment.
Q7: Can this vaccine be given with other vaccines?
A: Yes, it can generally be administered concurrently with other vaccines, but at separate injection sites.
Q8: What should I do if a patient experiences an allergic reaction?
A: Immediate medical attention is required for allergic reactions, particularly anaphylaxis.
Q9: Is this vaccine effective against all types of typhoid?
A: This vaccine only protects against typhoid fever caused by Salmonella Typhi, not Paratyphi A, B, or C, or non-typhoidal Salmonella.
Q10: When should this vaccine be administered before potential exposure?
A: Ideally, administer the vaccine at least 2 weeks prior to potential exposure to S. Typhi.
